Call out and cancel it immediately. Why can the other party receive SMS reminders?

It is because in modern communication technology, telephone and short message are transmitted in different ways. When you make a call, the communication network will automatically establish a call connection and send a call request to the other party. If you cancel the call before the other party answers, the call request will be terminated and the actual voice call connection will not be established. Therefore, the other party will not hear your voice, but will only receive the notification of the call request.