How to operate the number change notification function?

Step 1, confirm that the new number (which must be a telecom mobile phone number) has handled the communication assistant (call reminder) service, while the old number (which can be a mobile phone number, a Unicom phone number or a telecom mobile phone number, but cannot have the communication assistant service) has no communication assistant (call reminder) service; Step 2, the new mobile phone sends the old number to106591141by SMS to confirm the receipt of the SMS; Step 3, according to the prompt on the short message, call the corresponding customer service phone at the old number to open the call forwarding function for free, and do the corresponding call forwarding setting operation. 1) If the old number is a mobile user, the new mobile phone receives a short message: ":Change the number to inform that the voice function has been activated, please confirm that the call forwarding function of the old number has been activated (free of charge), and dial * * 21* 05512817256 # with the old number." 3) If the old number is a telecom user, the new mobile phone receives a short message: "The call forwarding function of the old number is enabled (free of charge), please confirm that the call forwarding function of the old number is enabled, and"