Hello Iphone geeks of sajha.

I  bought a used iphone3. Before buying it, I tried my at&t sim in it and it was working. After I took it to home, I connected to my computer to charge and itunes said that the firmware is old and needs update. I updated the IOS (but I didnot pay attention to which IOS it updated). After update, the phone restarted and stuck in activation. Now I cannot activate it through wireless (it says the activation server is busy and try again, but I don't think this is due to traffic at activation server). When trying to activate through itune it says the phone does not have sim card although it has simcard in it. 
Could somebody tell me how do I activate the phone now? The worst part is, I dont know which carrier it is locked to and which IOS version it has. 

Thanks in advance for your help.