Very Disappointed Customer

I paid up an account with Nimble on the 23/07/2021 which was handed over from Vodacom. I have been waiting for a paid up letter since then. I keep calling them and just keep being cut off. The account is still showing as if I still owe and was told on numerous occasions that I will be getting a paid up letter soon. The email address is ***. How can my account be handed over else where if I have already paid in full? Can I please have my paid up letter ASAP as you are messing up with my livelihood.