Buying a replacement phone off Ebay & putting in Sim card?

[xomalloryxo]

I had a Samsung Galaxy SIII. I had been experiencing problems (it wouldn't turn back on, would turn off randomly,etc) and I am not able to send it back due to their warranty policy. And I'm not paying 300$ to get it fixed or 500$ for a new one and I am NOT getting stuck into another two year contract with AT&T.

My friend has given me her old Samsung Galaxy S for a temporary replacement. I took it to the AT&T store and they gave me a new SIM card (the SIII has a micro SIM so I needed a new one) and activated it. I'm only using it for the time being.

If I purchase an AT&T phone on Ebay, will I be able to put my SIM card in and call my carrier and have them activate it?

 

[iHackPro]

Yep, as long as it's an AT&T Phone or unlocked GSM phone, you should be able to just pop in your SIM card and activate it no problem.

 

[xomalloryxo]

Thank you! But what does unlocked GSM mean? :3

 

[iHackPro]

The phone uses a SIM Card. Example, an LG Nexus 4 is an unlocked GSM phone because the phone is sold without contract and unlocked, and uses a SIM Card.