My Number: Unknown

[MM125]

I was trying to back up my phone today, but something went wrong. It backed up properly, but my phone ended up in recovery mode. After a few attempts, I restored it, and everything's working, except that under Settings>Phone, it says that my number is "Unknown" And I have no service, and can't call anyone. Does anyone know what the issue is?

My phone's a 16GB 4S.

 

[thesiren]

Sounds like your SIM card has jiggled loose. Open sim tray, check everything, replace, then hard reboot.

 

[MM125]

Well, I tried that, but I ran into a bit of a problem. I opened my SIM card tray, and there was nothing in there. In the year+ I've had it, I've never had a reason to open it. Do some carriers ship iPhones without removable SIMs?