Poor Service - Request for a paid up letter

I had a contract with CellC and paid up in 2017. My status was not changed to settled till I only found out in December 2020 when I was doing a property application. I requested for a paid up letter 04 December 2020, till today I haven't received it. I call them everyday to do a follow up, the only thing they tell me by Contracts department is that, they case is still pending. I am frustrated and angry at the same time as of today, the property was bought by someone else, because I took to long.