cancel_scheduled_message stops one scheduled template. It takes scheduledId from the schedule result. GreenTick refuses the cancel in the last minute before the message sends. A cancelled schedule is not a delivery, and a schedule that was never cancelled is not a delivery either.
Ask this
What the assistant calls
1
Read the schedule id
The assistant uses the
scheduledId returned when send_message scheduled the template. It does not guess an id.2
Cancel
cancel_scheduled_message runs only after you ask to cancel. If GreenTick refuses because the send is inside the last minute, the assistant reports that and stops.