Using T-Mobile iPhone X on AT&T

[AlphaGuitarist]

I'm an AT&T subscriber and, like many others, I preordered the T-Mobile variant to shave a few minutes off the process by avoiding carrier verification. I'm curious to know if setting up the phone with my AT&T SIM will lock it to AT&T. Since I bought the phone outright from Apple, eliminating AT&T from the equation, I would hazard a guess that it won't. Can anyone chime in?

 

[Djlild7hina]

It will stay unlocked so no worries 🙂 I did the same for the 6,7, and 8.

 

[AlphaGuitarist]

Thanks for the quick response!

 

[JonathanK81]

Question for you all. Do we need to even activate the phone with the T-Mobile Sim inside? Or as soon as we get the phone, we can remove the T-Mobile Sim and just pop in our AT&T Sim to activate it?