Getting a paid-up confirmation letter is a nightmare!!

Getting a paid-up confirmation letter is a nightmare!! On the 25th of September 2020 I called Cell C requesting the letter of a contract that ended in 2019, they promised to send it and they never did. I called on the 29th of September 2020, was promised that the query will be escalated to the supervisor. It is the 2nd of October 2020 today, I am still waiting....Tried to call *** (subscriber collections department) since 14:45, I can not get through, voice prompt keeps saying there is a technical problem. The customer care I am getting from Cell C makes me want to port my number. This is an inconvenience and a setback on my credit report because I am trying to buy property and the agent requires this letter.