I've lost access to mobile data on a Samsung Galaxy Nexus. Phone status reads 'disconnected from mobile network' and phone number 'unknown'. My account is active and fully paid. I can still make and receive phone calls. Wifi still works. I'm on prepaid for more than a year, and never had any problems until recently. I just can't access data away from wifi. The bars read grey. Resetting the phone briefly means the phone number will show up, but within a few minutes it goes back to 'unknown', and still no data access. I'm on Android 4.2.1, not rooted. Turning mobile data on/off/on, wifi on/off/on is no help. I'd appreciate any thoughts!