Vodacom refuses to stop billing my account after contracts have expired!

Our company has 4 contracts with Vodacom that expired 30 May 2021. I contacted Vodacom in April to inform them we would not be renewing the contracts. They told me to phone back again beginning of May to do the non-renewal. On 7 May 2021 I contacted Vodacom again and told them to please all 4 contracts. When we received our statement end of the month, they had only cancelled 1! I contacted them again to find out why they had not all been cancelled and asked for the amount to be credited. The consultant who helped me said she could see on the system that the request had been processed but not finalised. She would forward it through to head office to get it sorted out. We just received our latest statement yesterday, and again the 3 remaining contracts are still being billed to our account and the previous month's credit was also not put through! I gave more than enough notice that these contracts would not be renewed and yet Vodacom just refuses to cancel them. Don't know what more to do!