Are AT&T phones compatible with T-Mobile SIM cards that are unlocked?

[Kataryna]

I have an iPhone from AT&T that currently has a Net10 AT&T compatible SIM card. They have a new data policy that I can't use due to my work requiring countless hours on my phone, that also requires internet for different apps I use, but it's only for the AT&T cards. They offer free T-Mobile cards for compatible AT&T phones. Is the iPhone one of the compatible phones?

 

[JOSHUA]

It is! Your iPhone needs to be truly unlocked tho. Not one of these cheap unlocks that disappear if your phone is corrupted and needs to be restored. Apple offers them for 70 dollars that truly unlock your device. P.S my wife's name is Katarzyna so your cool!