Originally Posted by
Dread Pirate Jeff
Not an AT&T customer, but you should expect that to happen
(meaning be prepared for it). I was on the Verizon global unlimited plan for a number of years using my blackberry and first iPhone. Then they did the same thing. “oh, you bought a new iPhone? Sorry, that means you will have to have anew SIM and, sorry, no unlimited global data for you”.
Well, so far I've had three iPhones with the same ATT sim with my grandfathered Unlimited International LTE plan. iPhone 5S, iPhone 8, and my current iPhone Xs. It was all seamless- swap sims and voila- done. If there is any glitch moving to a 5G iPhone 12, then it will be the first time there was any issue. Fingers crossed. So far have not heard from anyone who made this move with my plan, so hoping to get some first hand reports.