I rang Apple and it turns out it is a software fault. Contact them also to log the fault and they will direct you to itunes on a PC/Mac to connect your phone to and restore the phone. This will put the latest bug-fix version (which is still 5.0.1, but a later sub sub sub version of it) on your...

i have the same problem intermittently which is combined with not being able to phone people (their end rings but we can't hear each other) along with complete texting failure as well, which means I never can send or receive texts while the fault is operational. I tried tintbob's suggestion...