Is there anyway i can stop using the orange tmobile service?

[Da?iel]

I started with this thing on orange, where it says i can switch to the tmobile network when i loose orange service or somthing like that anyway, however i am fed up of it only offering 2g networks, and wandered if and how i can stop using this "orange tmobile" stuff, and just use plain orange to get my 3g back? please help