Account paid up

I had an account from 2016 at the fashion express my account was then handed over due to no payments, I paid up the account and requested a paid up letter when I got one I lost my phone and I changed my emails now when I call for paid up letter and check on my clear score I still owe the store R298 I don't understand how because the first paid up letter said 00... when I call customer service I don't even get a response. How do I deal with this because now it's blocking my thing😡😡😡😡😡