While I should have acquired the Pro Max, I chose the Pro for cost savings which was a mistake. However, the 12 Pro will function as a SIP? phone, and the number is active. The reason for the larger display is it works for me. I am able to put it into a dedicated phone pocket which is nice for when I am not expecting IM? messages. However, if I was to acquire the 12 Pro Max, I wouldn’t have acquired the 14 Pro Max. If I would have acquired the 12 Pro Max, then it would have remained as my cellular phone. With that said, I would have had to replace my SIP Phone immediately when it expired.
The 12 Pro does not have a SIM? card installed. I am using a SIP client to make and receive calls with the 12. The iPhone 12 will remain as my SIP phone for the foreseeable future.