After upgrade to ios 6.1on iPhone 4S all calls go to voice mail
On January 29 I upgraded my iPhone 4S to ios 6.1. Since that upgrade all calls are going straight to voice mail without ringing.
Forwarding is not on.
The phone is not on mute.
I have 3 bars or better on signal.
Outgoing calls work fine.
The ringer volume is set to maximum.
When I place a test call to the phone from a landline it goes straight to voice mail.
This problem did not exist before the upgrade.
Any ideas or suggestions on other things to check?
IOS version is 6.1 (10B142)
iPhone 4S, iOS 6.1