I don't know, but you can try any of the following in an attempt to fix the problem:
1. Call your wireless carrier to see if there's a service issue in your area.
2. If there is no service issue in your area, ask the Verizon rep to see if he or she can troubleshoot the problem from their end.
3. Try rebooting your phone.
4. Go to Settings - General - Reset and then select "Reset Network Settings".
5. (As a last resort) Restore your device and set it up as new.