Not turning on or charge

The Galaxy S2 is an older phone, and you may find difficulty finding a repair shop that will fix it for you. You would probably be looking at $60-80 for a repair, but it's unlikely that they'd have the part in stock. Unfortunately, that's roughly the cost for a used Galaxy S2, so if you don't need to fix the phone to get your data off the phone (always back up your data! Use something like Dropbox or Google Drive), I would just get a new one.

I would try calling a few local repair shops in your area, but you're likely going to have to wait a while to get it fixed. Talk to T-Mobile and see if they can get you hooked up with a loaner phone.