"No SIM installed"

We got our iPhones Thursday. They are very cool, however, mine arrived with one of the glitches (of course). From the time I turned on my phone, I have been getting a message that there is "No SIM installed." So, we tried simply rebooting the iPhone. Success! (for an hour). Then we went to the AT&T store Friday to see if they could help. The salesman took out the SIM card, cleaned it off, because he said it had a giant oily fingerprint on it. I was good for about a half hour, then the message appeared again. We returned to the store. They replaced the SIM card thinking maybe that would help. It did for about an hour. We called the store hoping that I could just get a replacement, but they can't do that, so they directed us to Apple's iPhone hotline. So we called Apple for support. Derrick spent about an hour on the phone with a very helpful person who is going to send us a new tray for the SIM card. So, essentially, after waiting a very long time to get a smart phone (I have had the 1st generation RAZR for over 5 years now), having spent $300 on said smart phone, and increasing our monthly cell phone bill by about double, I can't make or receive a call or send or receive a text to save my life. What an awesome deal! I'm not exactly what you would call a happy camper right now. We'll see what happens when I get my new tray....