I can absolutely help you with your payment arrangement. Processing it through the T-Mobile app will save you $10 if we process it on this chat.  Just follow this step:
1. Open the app and tap BILL.
2. Tap Set up a Payment Arrangement. 
3. View the Set Payment Arrangement schedule presented
4. Tap Payment Method. 
5. Tap Continue
6. Read the Terms & Conditions and tap Agree & Submit.

https://www.t-mobile.com/support/account/payment-arrangement