Good question, also it was only a remark that the phone number or email address is not owned by the IM system. They can change anyway. I got my mobile number i

Good question, also it was only a remark that the phone number or email address is not owned by the IM system. They can change anyway. I got my mobile number in 1999 and already switched twice with the number. Sadly it is kinda expensive to take the number with you, 25 to 30 euros.