Its not a 4s I just bought it from someone to potentially resell. Not sure if i should use it though. Can it be converted to att?

nope. its cdma while att is sim card.

http://www.att.com/shop/wireless/devices/smartphones.html

there are clearly a few iphones on the AT&T site so, yes you can use the iphone 4 with AT&T if you wanted (verizon is better though) assuming that the phone is unlocked.

the att iphone=/=verizon iphone.

iPhones are locked into carriers for the most part, there are some exceptions though. Sounds like your phone is incapable of GSM if it is made for CDMA

http://support.apple.com/kb/HT1937

The iPhone 4 came in either CDMA (Sprint/Verizon) or GSM (AT&T) but not both. You cannot use a Verizon iPhone 4 on a GSM network as it doesn't even have a physical socket to plug in a SIM. The iPhone 4S has both GSM and CDMA radios and can work on either type of network if it's unlocked.