WhatsApp reminders: what the Business API will and will not let you do
You cannot send whatever you like. Any message you initiate has to use a template approved in advance, and templates that read like marketing get rejected. Write them as the factual notice they are — amount, date, reference — and approval is usually quick.
The 24-hour window is the rule that shapes everything. Once a customer replies, you can talk freely for a day. Outside that, you are back to templates. Flows that assume a free-form conversation at any time will break in production.
Messages are charged per conversation, not per send, and the rate depends on who started it. Utility notices are cheap. Designing your reminders as utility rather than marketing is both cheaper and more likely to be approved.
The practical upshot: use WhatsApp for the notice and give people somewhere to act — a payment link, a reschedule button. Trying to run the whole support conversation inside a template flow fights the platform instead of using it.
