I've just tried this. Switched too 2G, opened up a image and resource heavy website, tried calling and all I got was "this number is unavailable."

This could prove annoying in areas with limited signal and being connected too a service transferring data all the time!

I'm on T-Mobile UK. Tried it with 3G, and it worked fine whilst loading the same website.

Do you think it's possible monitor for calls, and cut out data to allow the call to come through?