Failure to refund money

Vodacom has incorrectly billed me for over R11 000. I have contacted their call centres multiple times and have clearly informed them to refund me into my bank account (from which I run a debit order). Instead they credit my Vodacom account and I now have to dip into my savings to prevent my bank account from going into an overdraft. As such I am losing out on daily interest from my savings account. I have contacted Vodacom so many times and each time it's an empty promise to refund my money. Will be going the legal route soon. Ever since I took out a new contract with them in January, my billing has been incorrect. Please look at your Vodacom statements CLOSELY!!!!