What's the difference between voicemail and SMS?

Hello: Voice short message is a way to record your own voice through the operator's voice storage device through a mobile phone and send it as a short message. It is used to receive and store such voice files, which is convenient for you to find and play or playback at any time. Calling 12536 can only talk for 36 seconds, which is the time difference set by the operator. How can people make money if you are allowed to record unlimited? If there is no restriction, there is no need to make long-distance and international calls. Record what you want to say 10 minutes and send it back. How to make money when the other party records 10 minutes? Do you understand my explanation? I hope I can solve your problem.