Internet enabled phones missing calls

After a particularly bad spell of missing four calls from Caroline, I wondered what was going on. I upgraded my Hero to the latest Modaco build and radio which seem good, but not staggeringly faster. While investigating, I discovered that most modern phones can’t use 2G data and make a phone call at the same time. This is kind of staggering in that it is ridiculous for an always on, always connected device, but I guess is a function of how the networks were set up in the first place: no-one expected always on data at the time (and the networks can’t really afford it today). My problem at home is that 3G signal is variable, so the phone keeps
hopping between 2G and 3G and that also kicks the phone off the network
to receive calls.

In summary: if I’m downloading data from a web page or email using 2G (G or E on the data network indicator) at the time that someone else phones me, the call will go straight to email and I won’t know unless they leave a message.

There is a free service from O2 that SMSes you if you have missed a call: I’m hoping this will mop up some of the occasions, but I’m not really sure how to fix it other than to have a phone that doesn’t do data.