Two-way SMS is messaging in both directions: your organisation sends to customers, and customers can send back — a reply, a keyword, a vote, a question. Inbound messages are called MO (mobile-originated) or P2A (person-to-application); the outbound ones you send are MT (mobile-terminated).
What two-way SMS is used for
Opt-in campaigns
"Text JOIN to 388" on a poster, a radio spot or a receipt builds a consented marketing list without a form.
Confirmations
"Reply YES to confirm your appointment on Tuesday at 10:00" — the reply lands in your inbox against the conversation.
Surveys and votes
A keyword per option lets members vote or rate a service from any phone.
Citizen and member feedback
Councils, utilities and NGOs take reports and questions by keyword, routed to the right team's inbox.
Opt-out handling
A STOP keyword brings opt-out requests to you so the numbers can be blacklisted and suppressed from future sends.
Customer support
Threaded conversations let staff reply to a customer's message from the dashboard.
How inbound messages reach your account
Inbound messages arrive on a number the platform holds — the shared short code (388) or a long number. Because many organisations share those numbers, the platform has to decide whose inbox each message belongs to. Ontech BulkSMS uses two rules, in order:
- Keyword match. The first word of the message is compared, case-insensitively, against the keywords registered on the platform. If it matches your keyword, the message is yours regardless of anything else. A keyword can be scoped to one destination number or apply to any.
- Reply window. If no keyword matches, a message from a number you recently sent to is attributed to you as a reply, and threads into the conversation with that contact.
Keywords are therefore the reliable way to run a public campaign on the shared short code: "text VOTE to 388" reaches you even from people you have never messaged. Keywords are unique per number, so they are registered on request; contact info@ontech.co.zm with the word you want.
Reading and replying
Inbound messages appear in your Inbox and in Conversations, where messages to and from the same number are threaded so a reply reads in context. Staff can answer from the dashboard or the mobile app; the reply is a normal outbound message, charged in credits and tracked with a delivery report like any other.
Two-way over SMPP and the API
Integrators do not need the dashboard. If you bind to the SMPP server as a receiver or transceiver, inbound messages for your account are pushed to your session as deliver_sm PDUs — the same channel that carries delivery receipts — so your software can react to a reply in real time. Outbound replies go back over the same bind or through the HTTP/JSON API.
Designing a keyword campaign
- Choose an obvious word. JOIN, YES, VOTE, HELP. Avoid words that other campaigns on the same number are likely to want.
- Say what happens next. "Text JOIN to 388 to get weekly offers. Standard SMS rates apply. Reply STOP to leave."
- Acknowledge every message. Send a confirmation reply — it doubles as the consent record the customer sees.
- Record consent. Add opted-in numbers to a contact group named for the campaign, with the date, so your marketing list is provably consented.
- Respect opt-outs. Route STOP to your inbox and blacklist those numbers promptly; the blacklist suppresses them on every future send.
Two-way SMS for Zambian organisations
The most common two-way use in Zambia is not marketing but participation: a church letting members text JOIN, a cooperative collecting votes, a council taking service reports, a health programme confirming appointments. The NGOs and churches and government guides show how those organisations combine keyword inbound with bulk outbound on one account.