I have this HTC incredible s from T-mobile which has all the frequencies. In the past we never had any problem, we unlocked it and were able to use it on any canadian network including wind and mobilicity. For some reason after unlocking ( code unlocking) its not working on bell. I never got chance to try telus which is also 3g network. I have tried it already on rogers , mobilicity, Fido but bell.
My HTC Incredible S worked perfectly fine on Bell network. I suspect that something is wrong with your SIM card? You could also try bringing it to Bell. Or you can try purchasing another SIM card from the Source or something for like $5 and see if it works.
Also, just because something is from T-Mobile doesn't mean it has all the frequencies....