My iPhone doesn't ring - keeps going to voicemail!?

Called O2 customer support.
I asked "My callers keep being diverted to voicemail. My phone does not ring even with all bars? I've even called it at my desk and can repeat the problem. I don't even see the missed call come up - what is going on?"
O2 " Yes sir we are aware of the problem. Do you use YouTube or browse the web much? do you use email push? do you use email polling?"
" Well yes but not all the time- what does that have to do with it, that's data and my calls are over normal voice circuit swtich - no?"
O2 " Well actually no sir - the iPhone can't handle a voice call and a GPRS connection at the same time"
"Ay?"
o2 "Yes Apple and O2 are aware of it and we are working on it. Actually you really need a good voicemail service so you dont miss any calls"
"You are kidding right?!??!??! What about 3G?"
o2 "That's a third party. We recomend you set up voicemail"
"Your voicemail does not support missed calls when my callers dont even leave a voicemail - so how do I know when I've missed a call in this scenario?"
o2 "ehm.. i'll make a note of that!"

This has to be a herring rouge?

I don't want to use this to plug HulloMail - but seriously if you have an iPhone on o2 and you dont want to miss a call well you know where we are!"