What are the costs?
We do not charge any monthly fees or setup costs for using the HTTP API. Only when messages are sent, the cost of that message is deducted from your SMS credit.
Each country (even each operator) has its own cost, as can be seen on the pricing page (linked below). Please check your message destination(s) for pricing information.
When a message is submitted to the HTTP API and an "OK xxxx" response is received, credit is deducted from the account.
When an "ERR xxxx" response is received, no credit is deducted.