HT4157: AT&T: How to set up and manage a cellular data account on your iPadLearn about AT&T: How to set up and manage a cellular data account on your iPad
Currently Being ModeratedFeb 27, 2013 9:19 PM (in response to clindquist)
SIM cards also can be broken or damaged. I advice you to eject the SIM card, clean the surface with an eraser
and place it again into the device. If the problem persists, contact your carrier to replace for a new one.
Hope it will be helpful