Orange iPhone 3GS Missed Calls/Calls Straight to Voicemail / O2 iPhone Full strength signal

I've read many reports that people with the O2 iphone or Orange iphone have found that calls are going direct to voicemail when they are in an area with full or very high strength network signal.

It appears that what is happening is that when the iphone is connected to the network in 2G mode (GPRS/EDGE) it is only able to handle either a voice call OR a data call but not both together. So when your phone connects to check your email,Facebook status, Ebay app updates etc it is then not able to receive calls. As this is happening in the background you have no real way of knowing what you phone is doing unless you are watching it all the time. And as the 2G network is so much slower than 3G it means the data connection will take that much longer and therefore mean you are out of contact for an even longer period of time.

This only happens when the phone connects on 2G (GPRS/EDGE) not with 3G connections which can handle both voice and data connections at the same time.