Bad service and i need my paid up letter

Bad service! I made a payment last year August for my contract phone however they stated that they didn't recieve it and asked for proof of payment of which i emailed and also sent to them through watsapp till today (2021.01.30) i still haven't received a paid up letter on top of that i have been transferred to other attorney's because i don't have a paid up letter and the call center agents all have different answers to my problem