Is this my SIM or my phone?

[Anglican-Mac]

For some reason, my phone keeps telling me I have no SIM card installed. Each time I will eject the SIM tray, make sure the SIM card is securely in it's tray, and then place the tray back into the phone. The phone is happy for awhile and then will tell me again.

I have an iPhone 3G on ATT in the United States, if this helps to diagnose.

Thanks in advance for anything anyone can tell me.

 

[brandon.8602]

if you have dropped your phone, you may have bumped it in a way where you messed up the tray mechanism causing it to come loose. I would say it's the phone and not the SIM card.