About the solution of short message gateway?

Then you are equivalent to the role of SP, and the rate is set by yourself. You say 2 yuan, then the operator will set the rate as 2 yuan. If a user uses your service, the operator will charge you according to 2 yuan (on your behalf). Of course, the premise is that you have signed a contract with the operator.

Because SMS is divided into uplink and downlink, sending 1234 to your code "5678" is uplink, and then you send a message back to 1234 through "5678", which forms a downlink operator, and only needs to collect downlink data at the SMS gateway (of course, your own platform also records it), and then settle according to the collected data and the SMS fee charged.