Money owed to customer

I returned a device an sim card within the cooling off period at the beginning of February 2021. On the 17th of April I realized that I was still being charged for this. I requested that this be cancelled and was told that I would be reimbursed for the 3 months that I was charged. On the 1st of May an amount of R 10460.00 was deducted from my bank account which included my standing contracts, the credit for the 3 months of the returned contract plus I was charged the full cancellation fee. I have been trying since then to get the amount of R7000 odd rand back from Vodacom with no luck at all. Now I am incurring interest charges from my bank because I have to use my credit card to cope. What am I to do to get my money out of Vodacom?