bulk SMS your customers can reply to.

Pick who. The audience is a contact list you import or already have in heysteff; each message goes to the contact's phone.

Pick what. A fixed text, the same for everyone, or a message the AI agent writes for each contact using their context. When the AI writes it, it's asked to keep it short, because in SMS every character counts.

Pick when. The campaign can go out at a scheduled date and time, fire on an event (an order, for example) or be launched from your system through the API.

See the cost first. The campaign review shows what it will cost based on each message's segments and tells you how many SMS you can send today. The cost is billed after sending, to your plan's card. If the campaign exceeds the daily cap, what fits goes out today and the rest goes out tomorrow, when the cap resets.

Automatic opt-outs. Anyone who replies STOP, BAJA, CANCELAR, SALIR or NOSMS is unsubscribed, and heysteff blocks any later SMS to that contact. The opt-out is recorded even if your number is in campaigns-only mode.

Quiet hours. Anything that would land in the middle of the night waits until morning, in your workspace's time zone.

Per-contact cap. Someone who already got campaigns today doesn't get another one, even if they're on several lists.

Paced sending and a daily cap. Messages go out at a steady pace, not all in the same second, and there are two daily caps: 1,000 segments per number (adjustable) and 500 SMS per workspace (support raises it if you need more), so a mistake can't turn into a large bill. Messages only go to your workspace's enabled countries; recipients elsewhere are left out and the review tells you how many.

This is the difference from a traditional bulk SMS provider. Campaigns go out from your two-way number, so a reply like "do you still have it in stock?" opens a conversation in your inbox, with the contact's name and history. Your team can pick it up, or the AI agent if you've turned it on for SMS.

A campaign stops being a blind blast and becomes the start of a sales conversation.

There are two costs and both are visible. The SMS number costs USD 5 a month (USD 60 a year on annual plans), added to your plan. Sending is billed afterwards to your plan's card, every time usage reaches USD 20 plus whatever is left at month end; there's no balance to top up. In Chile, each segment costs USD 0.021. A segment is 160 characters, or 70 if the message has accented vowels like á, í, ó, ú or emojis.

Campaigns are available from the Pro plan, with unlimited campaigns. On Starter you get the number and SMS conversations, but not bulk sends.

They don't compete; they complement each other. WhatsApp allows photos, buttons and catalogs, but anyone who hasn't written to you in 24 hours can only receive a template approved by Meta. SMS is text only, but it goes out without prior approval and reaches any phone, whether or not it has WhatsApp. In heysteff both kinds of campaign use the same guardrails and replies land in the same inbox.

You may also find useful: two-way SMS, automation flows, copilot mode and pricing.