Asking the telco to do this would not solve your problem. The biggest issue with 2G is that the base stations are relatively cheap (approx. £600; this is from someone who gave a talk at Over The Air) and, loaded with OpenBTS, can allow an attacker to set up a nefarious 2G base station wherever they want. Unless you can lock the phone down to only use 3G, or to only use certain base stations, you have a problem.
Here is a rather good video from Chaos Computer Club Congress which explains a lot of the details of how mobile phone networks work (I've been to other talks where they've demonstrated 2G highjacking with an OpenBTS base station). It can get very technical (and there are a grotesque number of acronyms) but may help with anything mobile.