Usage-based communication APIs in India bill voice per connected minute (rounded up to a pulse), SMS per 160-character segment on DLT-registered templates at about ₹0.12–₹0.30 for transactional traffic, and WhatsApp per delivered template message at Meta's rate — ₹0.115 for utility and authentication, ₹0.8631 for marketing — plus any platform fee. For OTPs, alerts and reminders, a WhatsApp utility message and a one-segment SMS land within a few paise of each other, voice typically costs the most per contact, and for promotions WhatsApp costs more per send but reaches every opted-in customer, while promotional SMS is blocked for DND numbers and limited to 10 AM–9 PM.
This guide puts the three channels on one page for Indian founders, product heads and ops teams who want real per-unit costs with no monthly commitment. Every third-party figure below is a published or commonly quoted number, stated before 18% GST. Vendors and Meta revise rates, so treat the tables as a starting point and confirm the live rate card before you budget.
What usage-based pricing means for a communication API
Usage-based pricing means you pay only for messages delivered or minutes connected, with no fixed monthly platform fee. It is the opposite of seat-based pricing, where every agent login adds a monthly charge, and of plan-based pricing, where you pay a fixed subscription whether you send ten messages or ten lakh.
In India, "pay as you go" almost always means a prepaid wallet. You top up, each call minute, SMS segment or WhatsApp message is debited from the balance, and sending stops when the wallet runs dry. That sounds simple, but the per-unit rate is rarely the whole bill. A pay-as-you-go rate card can still carry:
- A minimum recharge — the smallest top-up the provider accepts.
- Number rental — a monthly charge for a virtual number (DID) or toll-free line on voice.
- DLT costs — operator-portal registration for SMS entities, sender IDs and templates, sometimes with a separate per-SMS scrubbing line.
- GST at 18% — added on top of every figure in this article.
- Currency — some global CPaaS vendors bill in USD, which adds forex and card fees.
A true usage-based plan is one where all of those are either zero or clearly published, so your cost in a quiet month falls close to zero. For the WhatsApp side specifically, our pay-as-you-go WhatsApp API guide breaks down how per-message billing compares with monthly subscriptions and per-seat CRMs.
Per-unit prices across voice, SMS and WhatsApp in India
Each channel bills on a different unit, which is why a fair comparison starts by naming the unit. Voice bills time, SMS bills characters and WhatsApp bills delivered messages by category.
| Channel | Billing unit | Typical India price (before GST) | Hidden adders |
|---|---|---|---|
| Voice (PSTN calls, IVR, OBD) | Per connected minute, rounded up to a pulse (15, 30 or 60 seconds) | Mostly quote-based; enterprise vendors scale contracts to call volume, numbers and seats | Number (DID) rental, pulse rounding, contract or platform fee |
| SMS — transactional and OTP | Per 160-character segment (70 for Hindi or other Unicode) | About ₹0.12–₹0.30 per SMS at volume | DLT registration, scrubbing charges, extra segments |
| SMS — promotional | Per segment | Cheapest SMS category per message (quote-based) | Blocked for DND numbers; only 10 AM–9 PM |
| WhatsApp — utility | Per delivered template message | ₹0.115 (Meta India rate) | Platform fee or per-message markup of the provider |
| WhatsApp — authentication (OTP) | Per delivered template message | ₹0.115 (Meta India rate) | Platform fee or per-message markup |
| WhatsApp — marketing | Per delivered template message | ₹0.8631 (Meta India rate) | Platform fee or per-message markup |
| WhatsApp — service replies | Customer-initiated, replied within 24 hours | Free on Meta's side | Some platforms still charge their own fee |
Two lines in that table deserve to be quoted on their own. Meta's India rate for a WhatsApp utility or authentication template is ₹0.115, which sits at or below the bottom of the transactional SMS range. And a WhatsApp marketing message at ₹0.8631 costs about 7.5 times a utility message, so the category you send matters more than which provider you pick.
Voice is the channel where published per-minute prices are hardest to find. Most voice CPaaS vendors in India quote per account, so ask for three numbers in writing: the per-minute rate, the pulse size and the monthly number rental.
Pay-as-you-go communication API providers in India compared
The table below lists providers our team has already priced in detail, with figures taken from their public pricing pages or common quotes. "Quote-based" means the provider does not publish a rate card; you get a price after a sales conversation.
| Provider | Channels | Pricing model | Monthly or platform fee | Notes |
|---|---|---|---|---|
| MSG91 | SMS, OTP, WhatsApp, more | SMS about ₹0.16–₹0.25 on volume tiers; WhatsApp at Meta's rate | ₹500/month WhatsApp Titan plan | Fixed WhatsApp fee beats per-message fees above about 5,000 messages a month |
| Gupshup | SMS, WhatsApp, more | SMS mostly quote-based, about ₹0.12–₹0.25 at volume | Quote-based | Broad product range; ask for the full rate card |
| Karix (Tanla) and Kaleyra | SMS, voice, WhatsApp | Enterprise, negotiated | Contract-based | Suited to high volume and bank-grade routes |
| Exotel | Voice, IVR, messaging | Enterprise quote scaled to call volume, numbers, channels and seats | Contract-based (verify) | Strong when you need IVR, a call centre and number masking |
| Twilio | SMS, voice, WhatsApp, email | Per-message markup in USD on top of Meta's charge; no monthly floor | None | Developer-first; India SMS usually several times domestic aggregator rates; forex applies |
| RichAutomate | WhatsApp Business API only | Client Pay: Meta's rate + ₹0.10/msg. SaaS Pay: ₹1.50 marketing / ₹0.50 utility | ₹0 setup, ₹0 monthly | Usage-only; INR billing; pair with an SMS or voice provider for fallback |
For a longer list that includes Infobip, Route Mobile and others, see our roundup of the best CPaaS providers in India. If voice and IVR are central to your stack, our Exotel vs RichAutomate pricing breakdown shows where an enterprise telephony contract earns its cost and where a usage-only WhatsApp layer is cheaper.
Cost per outcome: 10,000 OTPs, alerts, reminders and promotions
Price per message is the wrong yardstick. What you actually buy is an outcome: a login completed, a parcel delivered, an invoice paid, a sale made. The table below prices 10,000 of each job on SMS and WhatsApp using the published figures above. It uses ₹0.18 per SMS segment, a mid-range transactional quote, and RichAutomate Client Pay (Meta's rate + ₹0.10) for WhatsApp. All figures exclude 18% GST.
| Job (10,000 sends) | SMS, 1 segment | SMS, 2 segments | WhatsApp at Meta rate | WhatsApp with Client Pay fee | Voice |
|---|---|---|---|---|---|
| OTP codes | 10,000 × ₹0.18 = ₹1,800 | 20,000 × ₹0.18 = ₹3,600 | 10,000 × ₹0.115 = ₹1,150 | ₹1,150 + ₹1,000 = ₹2,150 | Voice OTP as fallback only; per connected minute (quote) |
| Order and delivery alerts | ₹1,800 | ₹3,600 | ₹1,150 (utility) | ₹2,150 | Rarely used; too costly per contact |
| Payment reminders | ₹1,800 | ₹3,600 (amount + link often needs 2) | ₹1,150 (utility) | ₹2,150 | Used for overdue escalation, per minute |
| Promotional offers | Lowest SMS rate, but DND numbers skipped | Same caveat | 10,000 × ₹0.8631 = ₹8,631 | ₹8,631 + ₹1,000 = ₹9,631 | Outbound dialling, quote-based; DND applies |
Read across the rows and a pattern appears. For one-segment English messages, SMS and WhatsApp cost about the same; the moment a message needs a second segment, WhatsApp becomes the cheaper channel. WhatsApp has no segment limit, so a Hindi OTP with a warning line or a reminder with an amount, due date and payment link still bills as one message.
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Utility messages sent inside an open 24-hour customer service window are free on Meta's side, so the WhatsApp column above is a ceiling, not a floor. Promotions are the exception: WhatsApp marketing is the most expensive per send, and you only pay it because a rich, clickable message to an opted-in customer usually converts better than a plain promotional SMS. On SaaS Pay, where RichAutomate bundles Meta's charge, the same 10,000 sends cost ₹5,000 for utility or authentication and ₹15,000 for marketing. Run your own mix through the WhatsApp API cost calculator to see both billing modes side by side.
Hidden costs that change the real per-unit price
Most surprises on a communication API bill come from line items that never appear in the headline rate. Check each of these before you sign:
DLT registration and scrubbing (SMS and voice)
Every commercial SMS in India travels on TRAI's DLT framework. Your entity, 6-character sender IDs and every template must be registered on an operator portal before a single message goes out. Some portals charge a one-time or annual entity registration fee, commonly around ₹5,000 plus GST, and some vendors bill scrubbing as a separate per-SMS charge.
Unicode segments
One SMS segment holds 160 plain-text characters, but only 70 when the text contains Hindi, Tamil or emoji. A vernacular message can cost two or three times the English version for the same content.
Voice pulse rounding
A 20-second call on a 60-second pulse is billed as a full minute. On a 15-second pulse it bills as 30 seconds. For short IVR confirmations, pulse size can matter more than the per-minute rate.
Number rental
Voice needs a virtual number or toll-free line, usually rented monthly. That rental is a fixed cost even on a "usage-based" voice plan.
What counts as billable
Meta bills WhatsApp templates on delivery, so a message to an invalid or non-WhatsApp number is not charged by Meta. SMS billing on submission versus delivery varies by vendor and route, so ask which one applies to your account.
Minimum recharge and currency
A high minimum top-up locks cash in a wallet. A USD-billed provider adds forex, card charges and exchange-rate swings to every invoice.
DND, TRAI rules and compliance by channel
Compliance cost is part of channel cost, because a message that is blocked or a sender ID that is suspended earns nothing. The rules differ sharply by channel:
| Channel | DND scrubbing | Registration | Consent rule |
|---|---|---|---|
| SMS | Yes — promotional SMS is blocked for DND numbers | DLT: entity, sender IDs, templates | Explicit consent records needed for service-explicit traffic |
| Voice | Yes — commercial calls fall under TRAI's TCCCPR rules | Registered numbering series and DLT for telemarketing | Preferences of DND subscribers apply |
| WhatsApp Business API | Not DLT-scrubbed | Meta business verification and approved templates | Recorded opt-in under Meta's policy before sending templates |
WhatsApp sits outside DLT, but that is not a licence to message anyone. Meta requires opt-in, reviews every template and lowers your quality rating when users block or report you. Our explainer on whether DND and TRAI rules apply to WhatsApp covers where the lines fall today; regulations evolve, so check current TRAI guidance before a large campaign.
Which channel to use for which job
No single channel wins every job. These decision rules hold for most Indian businesses:
- OTPs: send on WhatsApp first and fall back to SMS only if the WhatsApp message is not delivered within a short timer. You pay SMS only on the failures. Our WhatsApp OTP vs SMS OTP comparison covers delivery speed, autofill and DLT side by side.
- Order, delivery and payment alerts: WhatsApp utility templates, because there is no segment limit and customers can reply in the same thread.
- Urgent, elderly or vernacular audiences: voice, where a spoken message beats any text for clarity.
- Rich content and two-way support: WhatsApp, with buttons, catalogues, documents and a shared inbox.
- Legal or regulatory notices: SMS plus email, where a carrier-logged record matters.
The most cost-efficient stack for many teams is hybrid: a WhatsApp-first layer for alerts, reminders and support, an SMS route for fallback and DLT-mandated notices, and a voice provider kept for escalations and IVR. You pay each channel only for the jobs it does best.
How to compare CPaaS providers fairly
Rate cards are built to look cheap. Use four rules to compare them honestly:
- Normalise to cost per delivered outcome. Count segments, pulses and category, not "messages".
- Add every fee. Platform fee, number rental, DLT, minimum recharge, forex and 18% GST belong in the total.
- Test on your real templates. Send your actual OTP and alert text through each shortlisted route and time delivery.
- Price a quiet month and a peak month. A fixed fee looks small at peak volume and large in a slow month; usage-only pricing scales both ways.
For SMS rates across Gupshup, Karix, Kaleyra and others, see our SMS API pricing guide for India. For RichAutomate's own rate card, including the optional Starter (₹499/month), Pro (₹899/month) and White-label (₹1,199/month) plans for teams that need more seats or numbers, see pricing.
Ready to move your alerts, reminders and OTPs to WhatsApp on usage-only billing? RichAutomate runs on the official WhatsApp Business API with ₹0 setup and ₹0 monthly fees — pay Meta's rate plus ₹0.10 per message on Client Pay, or an all-in price on SaaS Pay. Start your 14-day free trial with 100 free credits.
Frequently asked questions
Which is cheapest in India: voice, SMS or WhatsApp?
Per message, a WhatsApp utility or authentication template at Meta's India rate of ₹0.115 sits at or below a one-segment transactional SMS at about ₹0.12–₹0.30, and voice billed per connected minute typically costs the most per contact. Once you add a platform fee the two text channels are close, but WhatsApp wins whenever a message needs a second SMS segment. Promotional SMS is cheaper per send than WhatsApp marketing at ₹0.8631, though it skips DND numbers. All figures exclude 18% GST.
What is a pay-as-you-go communication API?
A pay-as-you-go communication API bills you only for what you use: per connected minute or pulse for voice, per 160-character segment for SMS and per delivered template message for WhatsApp, with no fixed monthly platform fee. You usually pre-load a wallet that is debited as you send. Some providers still add a minimum recharge, number rental or registration costs, so read the full rate card.
Does DND apply to WhatsApp messages in India?
TRAI's DND scrubbing applies to commercial SMS and voice calls under the DLT framework. WhatsApp Business API messages are governed by Meta's opt-in and template rules rather than DLT scrubbing, so you need recorded opt-in before sending templates. Rules evolve, so check current TRAI guidance before a large campaign.
How is voice API pricing calculated in India?
Voice APIs in India usually bill per connected minute, rounded up to a pulse such as 15, 30 or 60 seconds, plus monthly number rental. Enterprise CPaaS vendors often add a contract or platform fee scaled to call volume, numbers and seats. Many publish voice rates only on request, so ask for the per-minute rate, pulse size and rental in writing.
Is RichAutomate a usage-based WhatsApp API?
Yes. RichAutomate is a WhatsApp Business API platform with ₹0 setup and ₹0 monthly on usage-only billing. On Client Pay you pay Meta's rate directly plus ₹0.10 per message; on SaaS Pay it is ₹1.50 per marketing message and ₹0.50 per utility message all-in. It does not sell voice or SMS, so pair it with an SMS or voice provider for fallback.