What are the instructions for activating call waiting via SMS?

Hello, telecom users can edit SMS 650 or HJ and send it to 10001 to activate call waiting.

Call waiting means that when you are on a call and a third party makes a call, you can hear the "beep" call waiting tone. At this time, you can choose to hang up the previous party and answer the third party's call. You can also refuse to answer third-party calls, or you can answer the new incoming call after answering the current call (the other party has not hung up).