Vodacom dont cancel you contract at all

I have cancelled my contract over the phone at Vodacom call centre cancellations department, in August 2019 but the consultant never did the cancellation. I have lost my fone and needed to get a sim swop in October. I went to Vodacom shop in Alberton and requested the sim swop, but they could not help me before I pay an account of R760.00 for a contract they said was not cancelled. I asked them to phone for me a person that I can speak to at the cancellation department that would do the cancellation for me. The manager at the cancellation office promise me that the contract is now cancelled. Now this week, I get another message from Vodacom, saying they are blocking my number because the account has not been paid and I owe them contract fees for November and December. I phoned the cancellation office again today but the person helping me, said that he can not access my account because it is in arrears! How do I get this problem fixed?