REQUESTED REFUND OF MY ACCOUNT SITTING IN A CREDIT! No payment made

I recently cancelled my vodacom contract to move to prepaid. I received a bill at the end of July which I paid without question. Then after Vodacom realises that they made a mistake, my account is sitting in a credit of R588. I requested a refund on 16 Aug 2018 through the call centre. Reference 1- ********** ********** . Almost one month later my money has not been paid!