Phone application hangs up and stop receiving calls

[ayman]

hone: Dear All

Kindly advice me, I have i phone 4 with ios 5.0.1 and 3 times happen that my phone application hone: hangs up and doesn't respond to any calls,

when somebody calls me, it shows nothing in the interface and I can't replay for him, and when I call somebody it gives him the ringing tune but I can't here him and

can't here me too.


Please advice
My regards

Ayman