SMS your customers can answer: your number, your inbox, your AI agent.
heysteff is the AI platform for customer support and sales over WhatsApp, Instagram, Messenger, SMS, Gmail and Shopify; Steff is the AI agent that runs it. With the SMS channel, your workspace gets its own number that sends and receives text messages: whatever the customer replies lands in the same inbox as your chats, where your team or the agent can answer it.
◆ in one sentence
An SMS provider that doesn't just send: it receives the replies, organizes them in your inbox and can answer them with AI.
What two-way SMS means
Most bulk SMS is one-way: the message goes out from a sender that receives nothing, and if the customer replies, the reply is lost. Two-way SMS goes out from a number that also receives, so the reply comes back and the conversation can continue.
In heysteff that number is yours: each workspace gets its own, not one shared with other companies. Replies open a conversation in the inbox, next to WhatsApp, Instagram, Messenger and Gmail, with the contact's full history.
What you can do with the SMS channel
Chat from the inbox. Your team answers incoming SMS from the same inbox where they handle every other channel, and can start a new SMS conversation with a contact.
Let the AI agent reply. If you turn it on, Steff answers SMS with your information: catalog, policies and FAQs. It writes short, plain-text replies designed for SMS, and hands off to a person when needed.
Send campaigns. Messages to a contact list, scheduled or triggered by an event, with a fixed text or one the AI writes for each person. See SMS campaigns for the details.
Honor opt-outs. If someone replies STOP, BAJA, CANCELAR or SALIR, they're unsubscribed and won't get messages on that channel again. The system blocks it at send time, so nobody has to clean the list by hand.
See what happened to each message. Every SMS shows whether it's queued, sent, and whether the carrier confirmed delivery. If it doesn't go out, the inbox explains why: invalid number, unsubscribed contact, country not enabled, daily cap reached or a message that's too long.
How you get the number
You request it yourself in Channels → SMS, without emailing anyone. The number costs USD 5 a month (USD 60 a year if your plan is annual) and is added to your plan's subscription. It's available on paid plans billed by card (Starter, Pro and Max).
The number starts two-way: it sends and receives from day one. If you only want to send notices and not open conversations, you can switch it to campaigns-only mode; replies then don't open chats, but opt-outs are still recorded.
What sending costs
There's no balance to top up. Sending is billed afterwards to your plan's card: every time usage reaches USD 20, plus whatever is left at month end, on an invoice separate from your plan. Each message is charged according to its segments and destination country. In Chile, each segment costs USD 0.021.
There's no charge for incoming messages and no per-user fee. A message the carrier rejects isn't charged. If your card declines the usage charge, SMS is paused until it's paid, and we let you know.
Segments: why one message can cost more than one
SMS is billed per segment. A segment holds 160 characters in the standard SMS alphabet (GSM-7); longer messages are split into 153-character parts that the phone stitches back together. Some characters, like the accented vowels á, í, ó and ú or emojis, force a different encoding (UCS-2), and the segment drops to 70 characters, or 67 per part.
That's why heysteff caps each message at 3 segments by default (you can change it) and sets two caps: a daily segment cap per number and 500 SMS a day per workspace, with alerts at 80% and 100%. If you need more, support raises the cap. You also start out sending only to your store's country (or your number's); other countries are enabled on request. That way a configuration mistake or unauthorized access can't turn into a large bill. Before launching a campaign you see the estimated cost and how many SMS go out today.
Why SMS on top of WhatsApp
WhatsApp is where most of your customers chat, but not everyone has it and not everyone replies there. SMS reaches any phone, with no app, and doesn't depend on templates approved by Meta: you write the text and it goes out. It's useful for notices that can't get lost, for contacts who don't use WhatsApp and for campaigns to lists where all you have is a phone number.
What heysteff changes is that the SMS stops being a standalone message: if the customer replies, the conversation sits next to their chats from every other channel and the same team or agent handles it.
What it doesn't do yet
Better to say it before you find out: today the channel sends text only (no MMS, photos or files), uses phone numbers as the sender (no alphanumeric sender IDs or short codes), and priced destinations are in Chile. It also doesn't send from automation flows, cart recovery or review requests: SMS goes out through campaigns, the inbox and the agent.
Frequently asked questions
Is heysteff an SMS provider?
Yes. heysteff gives you your own SMS number that sends and receives text messages, and sending is billed afterwards to your plan's card. The difference from a traditional SMS provider is that replies don't get lost: they land in the same inbox as your WhatsApp, Instagram, Messenger and Gmail chats, and your team or the AI agent can answer them.
How much does it cost to send an SMS?
In Chile, USD 0.021 per segment. A segment holds 160 characters in the standard alphabet, or 70 if the message has accented vowels like á, í, ó, ú or emojis. The number itself costs USD 5 a month (USD 60 a year on annual plans), added to your plan. Sending is billed after it goes out, to your plan's card: there's no balance to top up.
Can the AI agent answer SMS?
Yes, if you turn it on for the channel. It answers with your business information, in plain text and short messages designed for SMS, and hands off to a person when needed. You can also let only your team reply from the inbox.
Which countries can I send SMS to?
Today, priced destinations are in Chile. Each workspace also sends only to its enabled countries: at first, your Shopify store's country or, without a store, your number's. Other countries are enabled on request through support. A message to a country without a rate or not enabled isn't sent, and the inbox tells you why.
When am I charged for the SMS I send?
After they're sent, to your plan's card: every time usage reaches USD 20, plus whatever is left at month end, on an invoice separate from your plan. There's no balance to top up. The number costs USD 5 a month and is on your plan's invoice.
Is there a daily SMS cap?
Yes. By default, 500 SMS a day per workspace, counted by your time zone's day, with email alerts at 80% and 100%. Each number also has a daily segment cap. If you need more, support raises the cap.
What happens if my card is declined for the SMS charge?
SMS for your workspace is paused, including messages sent by someone on your team, until the charge is paid. Your other channels keep working. You're notified in Settings → Channels.
What happens if someone replies STOP?
They're unsubscribed from the SMS channel. heysteff recognizes STOP, BAJA, CANCELAR, CANCEL, SALIR, NOSMS and NOMASSMS, and blocks any later SMS to that contact, including campaigns.
Can I send SMS with my company name as the sender?
Not yet. The sender is your phone number, which is exactly what lets customers reply. We don't offer alphanumeric sender IDs or short codes.
◆ next step
Create your workspace, pick a plan and request your SMS number in Channels. If you'd rather see it with someone, book a demo.
You may also find useful: SMS campaigns, copilot mode, automation flows and pricing.