*********** accounting on contracts

My account was arranged to be converted from an account (which is long past maturity date) to prepaid. The arrangements were done and processed by Jonas at cellc and they confirmed my switchover date as 13 November 2020. Account was paid up and i had already started buying prepaid to use service on my existing number.They are calling me from the collections re. An account in arears of R11k ! Absolute nonsense. I have recieved several call and requested the error be corrected. On last call from Gabriella at collections was not willing to help to resolve the matter and expects me to resolve the accounts dept. Incorrect account.