Knowledgeable person, Guangdong Telecom reminds you that the owner is on the phone, and we will inform our friends in Guangdong Telecom by SMS. What does this mean?

This should be a "call reminder" for telecom services. Maybe your friend didn't turn on the call waiting, so when you called, he happened to be talking to someone else. In order not to miss your call, the "call reminder" function of telecom is expected to play a role. It will send a message to your friend to remind him that you called him, so that when your friend has finished talking with others, he will call you back when he sees the text message.