When you call the other party, what you hear is that Shanghai Mobile reminds you that you will notify the other party in a short time whether it is turned off or on the phone.

Power off, the other party has turned on the SMS reminder function. When you open it, you will receive a short message telling you which calls you missed when you turned it off just now.

I started this function. Once I turned on my phone, I received a short message saying that there was a call at my home phone number 6312xxxxx, so I called back quickly.