Check your T-Mobile bill balance instantly, without making a call
You can check your bill balance any time you'd like -- without sitting through annoying voice recording prompts. Your bill balance, bill due date and most recent bill payment information will appear on your screen -- even better than receiving it via text message.
Dial #225# and press the Call button

I know what you're thinking! You are making a call. But read on..
Your bill information will appear on-screen

You will see a loading screen while T-Mobile is processing your information. After a few seconds, your requested information will appear.