How each channel works
SMS sends short text messages to any mobile phone, with no app or internet connection. In India a business registers its entity, sender header and message templates on the operators' DLT platforms before it can send commercial SMS. Bulk SMS covers promotional, transactional and OTP messages.
WhatsApp Business API lets a verified business message customers who use WhatsApp and have opted in, in a two-way conversation that can include images, documents and buttons. Business-initiated messages use templates approved by Meta. See the WhatsApp Business API service.
RCS Business Messaging shows branded, rich messages (cards, carousels, suggested replies) in the phone's messaging app for customers whose phone and network support RCS. Businesses send as a verified sender. See RCS Business Messaging.
The three channels side by side
| Factor | SMS | WhatsApp Business API | RCS Business Messaging |
|---|---|---|---|
| Needs an app or data | No app or data | WhatsApp app and internet | RCS-capable phone and network |
| Sender identity | Registered sender header (DLT) | Verified business profile | Verified business sender |
| Consent | Consent and customer preferences under TRAI rules | Customer opt-in required | Consent rules apply; confirm with your provider |
| Pre-approval | DLT entity, header and templates | Meta-approved templates for business-initiated messages | Sender verification and content review |
| Content | Plain text; a single message holds 160 characters of GSM text or 70 of Unicode | Text, images, documents, buttons | Rich cards, carousels, suggested replies |
| Two-way conversation | Limited | Yes | Yes |
| Pricing | Varies by provider, message category and volume. Ask for a written quote for each channel. Mantraxtel quotes on request. | ||
Which channel for which message
| Message | Usually best | Why |
|---|---|---|
| One-time passwords | SMS, with a voice call as a fallback | Reaches every phone fast; see OTP authentication |
| Order and delivery updates | WhatsApp for opted-in customers, SMS for the rest | See WhatsApp vs SMS for order updates |
| Customer support chat | Two-way, with files and a shared team inbox | |
| Offers with visuals | RCS or WhatsApp, with SMS for others | Rich content where the customer can see it |
| Urgent, must-reach alerts | SMS, plus a call if needed | No app or data needed |
Consent and approvals, channel by channel
Each channel has its own gatekeeper, and a message that skips it is blocked. For SMS, TRAI sets the registration, template, consent and preference rules; our guide to TRAI rules for business SMS summarises them. For WhatsApp, Meta's WhatsApp documentation describes verification, opt-in and template categories. For RCS, Google's RCS Business Messaging documentation describes sender verification and message types. Rules change, so check the source before launch.
Using the channels together
Most businesses do not pick one. A typical pattern is to send rich or conversational messages on WhatsApp or RCS to customers who can receive them, and keep SMS for critical messages and for customers who cannot. Before you rely on automatic fallback between channels, ask your provider exactly which fallback it supports and how it is billed.
Five questions to decide
- Must the message reach every customer, whatever their phone? Use SMS.
- Do you need a two-way conversation or attachments? Use WhatsApp.
- Do you want branded cards and buttons in the phone's messaging app? Consider RCS, with SMS for others.
- Have customers agreed to hear from you on that channel?
- Are your sender registration, templates and verification ready for that channel?
Sources: TRAI, Meta's WhatsApp documentation, Google's RCS Business Messaging documentation. Last updated . General information, not legal advice. Talk to the team about the right mix: book a demo.