Can you bring an unlocked iphone 4s to tmobile?

And also what plans can I get?

Added (1). I did my research on solevei. Its bs

Yes if it is GSM http://attiphoneunlocker.com/
Once you receive your email to confirm that your handset is unlocked, for the iPhone simply connect it to iTunes which will complete the unlock.

Once your Unlock has been processed just follow these simple steps:

1) Open iTunes on your Mac or PC (verify you have internet connectivity).

2) Connect your iPhone to your computer using the USB data cable.

3) Backup and Restore your iPhone using iTunes.

4) Once your iPhone is restored it will have the Factory Unlock in place!

There's a possibility the code will be returned as NOT FOUND and its not in our control. If that happens you will be refunded.
http://attiphoneunlocker.com/