Unless you have it unlocked and then you can put a t-mobile sim card OR a Indian/European/Asia/African sim card in it…

There are only 2 sizes of sim cards on Earth.. Size 1–credit card size… Size 2—thumbnail size…. the ATT standard is thumbnail size……however when we sell Sim Cards—they come already ’snapped" into the credit card size—just in case there is a customer still using a VERY VERY VERY old cell phone… to unsnap the thumbnail sim–simply push it out like a piece of a puzzle

but, agian, all ATT sims are trasnferable to all ATT phones
References :
att wirleless manager