Hi all, I'm after your expertise I have a new iPhone 5S and am having call problems. Seems that I'm not always receiving calls, many people have been trying to ring me and it goes straight to voicemail. I get no notification of a missed call or voicemail usually until I go to make a call. It seems this then unfreezes the phone and can then receive calls again. I've tested by getting someone I'm with to ring me and it doesn't ring and goes straight to voicemail! Any ideas how to see whether it's phone or network? Many thanks. PS I'm on O2 UK.