Please Post in the Introduction thread here:
Introductions
or i cannot properly assist you.
Also i need to know the following in order to help you correctly, please:
1. phone name like "huawei U8665 Fusion, etc:
2. carrier you have now:
3. Android OS 2.3.4/2.3.6:
and to clarify Just rooting it won't allow you to use a T-Mobile Sim, you may also need to Unlock it and do a number of things before it can function on an alternate carrier, if it even can.
but i will do my best to assist you.