Q: We have 2 Iphones, and at the same time they quit receiving/sending calls.  Can anyone help out?

We have two I Phones, and at the same time this evening they quit sending and receiving calls.  I had just turned my phone off and back on because I was having trouble sending texts but had been making calls before I turned it off.  After turning it back on, both phones were no longer sending/receiving calls.

Can anyone help with this?   We have one I Phone 4 and one I Phone 4S.