Convert SM-G920A to SM-G920T

is it possible to convert a Sim Unlocked AT&T Galaxy S6 to a T-Mobile Galaxy S6? with the Stock T-Mobile S6 firmware so i can get the T-Mobile features? and if so which stock rom is needed the phone at Android version 6.0.1 on it right now.

Thanks,

from xda-developers http://ift.tt/2ddyHxn
via IFTTT