Depends on the rate plan and type of prepaid services. I would suggest reaching out to care directly so they can verify if your account is eligible, and if so, why it's not working!
The T-Mobile app doesn't work for prepaid customers, period!
FOR A YEAR, the app kept displaying a screen "Were not ready for you yet." Really? AN ENTIRE YEAR?
NOW, it says "Something isn't right..." I'll say.
Believe me, it's been longer than a year! I had to use the site with my computer, and it works well for all that I had to do. There are the "short codes" that work for me.