can I activate a used unlocked gsm phone on att just by moving the sim?

[greyghost302]

Newbie needs new phone....but not smartphone

 

[hang-the-9]

Try it, if it works, it works. If not, then contact AT&T. I know I can move an AT&T sim from device to device and it activates, don't know if it will work the same for non AT&T devices.