Can I switch an AT&T iPhone to MetroPCS?

My friend is planning on selling her iphone to me once she gets a new one, but it s an AT&T phone and I ve heard of issues about some phones not being able to switch carriers? Can I get a simple answer for this?
Answers

BlkBear

Your friend gets the phone unlocked, BEFORE she leaves AT&T. Otherwise YOU pay a cellphone unlocking service to unlock the phone. Once you take the phone to MetroPCS, you ask for their current APN settings, enter them in the correct menu on your phone, and MMS and data will work properly for that phone on their service.

SRΛSC

Maybe a little tricky. Metro is a CDMA network though it was recently purchased by T-Mobile which is GSM, like AT&T. May depend on the iPhone in question as well.

Ladre

it just needs to be unlocked that's all