Choose a channel for each message, not for the whole business
Most businesses do not need to pick SMS or WhatsApp once and for all. The better question is which channel suits each message: the OTP, the fee or bill reminder, the order update, the festival offer. This article helps owners and office managers sort their own message list using four tests: reach, cost structure, permission and delivery reporting.
The short answer: SMS reaches almost every mobile number, including basic feature phones, and suits short, urgent alerts. The WhatsApp Business API suits messages that benefit from a document, a button or a reply, sent to customers who have agreed to hear from you on WhatsApp. Many organisations treat SMS as the floor that reaches everyone and WhatsApp as a richer layer on top.
Reach: who will actually receive the message
SMS needs only a SIM card and network signal. There is no app to install and no mobile data required, so it reaches a grandparent on a keypad phone, a delivery boy whose data pack has run out, or a parent in a village with weak internet. It also arrives when the customer has switched mobile data off to save battery.
WhatsApp needs the number to be registered on WhatsApp, a smartphone (or a linked device) and an internet connection at some point. A message sent while the phone is offline waits until it reconnects. If the number is not on WhatsApp at all, the message fails, and your delivery status will show that.
Avoid guessing what share of your customers use WhatsApp. Once you have opt-ins and start sending, the delivery statuses from your first few batches will tell you how many numbers on your own list are reachable there, which is far more useful than any national figure.
OTP, reminders, order updates and offers: where each fits
One-time passwords
An OTP must arrive within seconds on whichever phone the customer is holding. SMS remains the default because it does not depend on an app or data. WhatsApp offers authentication templates for codes, and some businesses add "Send code on WhatsApp" as an option, with SMS as the fallback when WhatsApp delivery fails.
Fee, bill and payment reminders
Both channels work. A short SMS with the amount and due date reaches everyone. WhatsApp can also carry the invoice as a PDF, a payment link button and a way for the customer to reply "already paid", which saves your accounts staff a phone call. If collections are a regular headache, our guide to credit control and outstanding collection covers the process behind the reminders.
Order and delivery updates
Multi-step updates (placed, packed, shipped, delivered) suit WhatsApp because they sit in one thread with a tracking link and the customer can reply with a question. SMS is still useful for the one step that must not be missed, such as the out-for-delivery message for a cash-on-delivery order. The wider checkout picture is in our article on UPI checkout for Indian online stores.
Offers and promotions
Promotional SMS does not reach numbers that have blocked promotional messages and is limited to certain hours. On WhatsApp, marketing templates can go only to people who have opted in, and customers who feel spammed can block or report you, which hurts your standing with Meta. On both channels, fewer and more relevant offers work better than frequent blasts.
How each channel is charged: structure, not rates
We do not quote rates here. They vary by provider and volume, and Meta changes its WhatsApp pricing model from time to time. What you need is the structure, so that you can compare two quotes on the same basis.
SMS
SMS is charged per message part. One part holds up to 160 characters of plain English text but only 70 characters when the message contains Hindi or other non-Latin script, and longer messages are split into several parts, each billed separately. A Hindi fee reminder can therefore cost two or three parts where the English version costs one. Ask whether you are charged for messages submitted or messages delivered.
WhatsApp Business API
Meta charges for template messages that a business sends, and the charge depends on the template category (marketing, utility or authentication) and the recipient's country. Meta used to count charges per conversation and has since moved to charging per template message; replies sent while a customer is actively chatting with you are treated differently from templates sent out of the blue. Check the current model on the WhatsApp Business Platform documentation before budgeting. Your provider will also charge for its panel, API access and support.
Questions to ask when comparing quotes:
- For SMS: is the charge per part or per message, for submitted or delivered messages, and how are Hindi (Unicode) messages counted?
- For WhatsApp: which Meta charges are passed through, are they billed by the provider or to your own Meta account, and what does the provider add on top?
- For both: are there minimum commitments, how long do prepaid credits stay valid, and do delivery reports or API access cost extra?
Permission to message: DLT rules for SMS, opt-in for WhatsApp
Business SMS in India must be sent from a registered header using a registered template in the correct category, and promotional SMS must respect the customer's do-not-disturb choice. Our guide to DLT registration and SMS compliance explains how that works.
WhatsApp's business messaging rules require you to get the customer's opt-in before you send business-initiated messages, and the customer should understand they are agreeing to messages from your business on WhatsApp. Keep a record of when and how each person opted in. Writing the templates themselves is covered in our separate article on getting WhatsApp templates approved.
An admission form, patient registration form or checkout page is the easiest place to collect both permissions: write the mobile number once, with one line for SMS alerts and a tick box for WhatsApp updates.
What delivery reports can and cannot tell you
An SMS delivery report shows whether each message was submitted, delivered to the handset or failed, usually with a reason for failure. Delivered means the phone received it; SMS cannot tell you whether the customer opened it.
WhatsApp statuses go one step further: sent, delivered and read, passed back to your panel or software through webhooks. The read status appears only if the customer has read receipts switched on, so treat it as a bonus signal rather than proof. Failure statuses, such as a number not being on WhatsApp, are the most useful part because they tell you who needs another channel.
These statuses make a fallback rule possible. For important alerts, send on WhatsApp first and, if it is not delivered within a time you choose, send the SMS version. This needs your software to read the status through the API and act on it. Use it only where the alert matters, otherwise you pay twice and risk sending duplicates.
Decision table: sort your own message list
Copy this table, replace the examples with your own messages, and decide one default channel and one fallback for each. Write the decision down so staff do not send on both channels out of habit.
| Message | How urgent | Needs document, link or reply? | Suggested channel |
|---|---|---|---|
| Login or payment OTP | Seconds | No | SMS; WhatsApp authentication as an optional extra |
| Student marked absent | Within the hour | No | SMS, because every parent's phone receives it |
| Monthly fee or bill reminder | Same day | Helpful: invoice PDF, payment link | WhatsApp to opted-in customers, SMS for everyone else |
| Order placed, shipped, delivered | Same day | Yes: tracking link | WhatsApp; SMS for out-for-delivery on cash orders |
| Appointment confirmation | Day before and same day | Helpful: map location, reschedule button | WhatsApp with SMS fallback |
| Complaint or service request update | Same day | Yes: customer may reply | WhatsApp, so the reply stays in one thread |
| Festival offer or new stock | Not urgent | Helpful: product image | WhatsApp marketing template to opted-in customers, or promotional SMS, but not both to the same person |
Running SMS and WhatsApp from one setup with MATROP
MATROP PRIVATE LIMITED offers bulk SMS (promotional SMS, transactional alerts, OTP, contact groups, delivery reports and API integration) and the WhatsApp Business API as separate services that can work together. For WhatsApp, we help you move from a normal WhatsApp number to the official API with a display name, prepare templates, set up chatbot or menu flows with handover to a staff member, and connect your website, ERP or CRM through the API and webhooks. Messages can go out from a panel or from your own software, with a record of what was delivered, so one event can trigger SMS, WhatsApp or a fallback between them.
You may not need both. If you send a few dozen reminders a month and customers mostly phone you anyway, a well-configured SMS route can be enough. The WhatsApp API starts to earn its setup effort when you send documents or payment links, want customers to reply, or have several staff answering the same number. Tell us your message types and monthly volume and we will say honestly which one fits.
Questions people ask
Can one event trigger both an SMS and a WhatsApp message?
Yes, if your software or provider panel supports it through an API. It is usually better to choose one channel as the default and use the other only when the first is not delivered, so customers do not get the same alert twice.
Will customers without WhatsApp miss our alerts if we move to WhatsApp?
Yes, unless you keep SMS for numbers that are not on WhatsApp or have not opted in. For essential alerts, keep SMS as the fallback.
Is the free WhatsApp Business app enough instead of the API?
For a small shop replying to customers by hand, the app may be enough. The API is meant for automated messages sent from software, approved templates and several staff sharing one number, which the app is not designed for.
Does a WhatsApp read tick prove the customer saw a reminder?
Only when it appears. Customers can switch off read receipts, so a missing read status does not mean the message was ignored.
