Brooks & luyt paid up letter

I Got a call from brooks, Spoke to a call centre agent in April about an outstanding credit card amount, they then offered me a discount, i then asked the arrangement set for this discount is to pay over a period of 3 months, i then asked if im able to pay it before the 3 months will that be okay and they agreed i then was able to pay the full amount within 2 months, we now in july and i keep calling to get a paid up letter but i was told the account handler did not request it, i then asked for it to be requested, after another 14 days im getting automated messages saying im still owing on my credit card but i keep getting told tp ignore the messeges, i then called today and the agent told me that the account handler did not check on the account and has not closed it thats why i keep getting messages that i am owing, each time i called it was escilated and everytime its sorry about the inconvinience with no solution.....then an agent tells me the system got a bulk payment the first month and readjusted the discount and made another arrangement of which i did not know of and im told the account holder should have updated it but did not.....iv made so many phone calls to Brooks i now dont understand.