Verizon could have lost service on the only tower close enough to you. Your phone could have gone bad. All we can do is guess. Call Verizon Mobile tech support (not customer support) and see if they have an outage in your area. If not, and they can't tell you which buttons to press to bring your service back, bring the phone into a Verizon store.
If this is a new phone or one recently switched to Verizon from another carrier, it's possible the APN settings are still in there from the previous carrier. Google "verizon apn settings <your device name or model>" and it should point you in the right direction.