Can't activate, no original carrier SIM
I have an AT&T iPhone 4 that my friend gave me once her contract was up. She contacted AT&T for them to unlock it which they did. However, when I try to activate it now, I get the message "We're sorry, we are unable to continue with your activation at this time. Please try again later, or contact customer care."
I do not have an AT&T SIM for the phone, nor do I have easy access to one (I'm currently in Cambodia). Can I activate the phone without an AT&T SIM? It seems like I should be able to since AT&T claims to have already unlocked it.
Any suggestions would be appreciated.
iPhone 4