PAID-UP LETTER NOT BEING RECEIVED

how on earth do i get hold of the right people to help me in this debt collection firm??? since i have paid up my standard bank credit card I've been told that this people will forward me a paid up letter stating that my account has been fully paid. so Since July 2021 I've started phoning this people to request my paid up letter so that I can send it to Standard Bank so that the default can be lifted from my name. it October already and 5 Requests has been lodged with this firm and still no paid-up letter. everytime i try to phone them and eventually get through they transfer me from 1 person to another. so how on this F### earth do i get hold of this people just for one letter that would make my life so much easier. and Standard bank can also do nothing about it since i must request my own paid up letter by a firm they sent my account to.