Vodacom are *******

On the 8th of June 2017 I cancelled a contract and paid R923,98 cancellation fee. On the 2nd of July, Vodacom debited my bank account with an amount of R609,00. This was the amount of the monthly contract charge but as the contract had been cancelled the debit was an error on the part of Vodacom. For the past two months I have been trying to get this amount refunded but to no avail! Vodacom will not abide by instructions or requests to refund the amount. I have been to the Vodashop in Stellenbosch Square on at least 6 occasions and whilst the staff there are very helpful and caring, Vodacom are the exact opposite. Please help me to get this ' ******' money refunded to me.