I have a XS Max. Bought a new 12 Pro Max. Current iPhone on ATT. New phone bought with ATT sim. Bought outright, unlocked. What is the best way to activate new 12PM? I want to ensure SIM card supports 5G, so thinking use new SIM card in 12PM. I want to avoid paying ATT any dumb activation fee. Same number. Also how do I know if current phone is using ESIM? Is it best to use ESIM so when you travel international, you can simply pop in new Physical SIM? Thx in advance.