Do I lose service if I reset my iphone (T-mobile)?

Do I lose service if I reset my iphone (T-mobile)?

No you shouldn't lose your service unless you haven't been paying! ;)
If you want to be on the safe side, take the SIM card out before you factory reset.
And make sure that you've backed up on iTunes, you should be able to transfer the data over… But I've only had the original iPhone.