Request for my payed up letter

I had a phone on contract with mtn I payed up the phone on 2022 I requested the account to be closed. Then recently when I check my credit score as I'm buzy with application of my bond I found out that I'm in arears with mtn and my account was sent to legal department with an amount of R235 and of which I never got any messages stating that i must pay anything.i ended up paying the amount and requested a payed up letter with no luck I am still waiting and they keep on promising that they will send it if when I don't know I am loosing patience now and I just feel like mtn has failed me. My email address *** cell no ***