iPhone 4s not activating fully with AT&T sim I bought a used iPhone 4s from eBay and, of course, when I recieved it, it was inactivated.  I put in an old At&amp;t sim I had in the house (not sure where it came from as I've never had At&amp;T), and I was able to get past the activation screen and enter some info and set up Siri and iCloud. 

However, it never actually gave me the message that is was now activated and when I try to put my sim from another carrier in, it reverts back to the inactive screen. It is not currently unlocked (I am attempting to complete that but must get past the inactive screen).  

I have the latest iTunes installed and I have tried doing a backup and restore from backup and also just a hard restore all after fully rebooting the device.

Is it the sim or am I doing something wrong?
What you describe is consistent with an iPhone that is still locked to AT&amp;T as the sole carrier. You can go to the AT&amp;T websites and fill out a form to see if the phone could be unlocked. If you can't get AT&amp;T to unlock the phone, then you could take that up with the seller of the phone or perhaps see about jailbreaking the device and unlocking it by force as opposed to by social convention.