Does an unlocked TMobile phone have the same quality as an ATT phone when using ATT sim card

You’ve likely heard different answers because it totally depends on the make and model of the phone. An unlocked T-Mobile iPhone would work exactly the same on ATT as an ATT locked iPhone or factory unlocked iPhone. The same is not necessarily true for all other phones. Whatever unlocked T-Mobile phone you are considering, you need to make sure that exact make and model is on ATT’s supported phones list.

Make and model are supported (one plus 8T, one plus 9 pro) and i know they work on all carriers but i was wondering if the T-Mobile phone will have the same signal strength( coverage and internet) as a regular unlocked phone or an ATT phone!

No reason why it wouldn’t. The unlocked phone should receive the same signal and coverage as an ATT or factory unlocked phone of the same model. 

Hello @Anis007, we can help you with your qeustion.

If you are wanting to know about the signal of T Mobile we will be glad to provide the information for you. You can reach them by calling 1-800-937-8997.

You can go directly to T Mobile site here.

Thank you for visiting AT&T Community Forums!

Danielle, AT&T Community Specialist

The model number provided isn't necessarily specific enough.  For the 8T, it needs to be KB2000, KB2001, and KB2005, for example.