Empty promises from Retention department and billing/accounts

Dont trust the Vodacom retention team's empty promises! Despite various promises to refund incorrect billings (>R1,000), Vodacom has after 4 months still not actioned it.

Wanted to cancel rather than renew my Vodacom contract but was convinced by the Retention Department to remain on contract and they promised me a great discounted deal. However, I was then firstly charged at normal rates and secondly incorrectly double billed for the month (as my prior contract was still active.) Despite various calls to the call centre and promises from staff and managers the incorrect billings and refunds have still not been actioned.

Every time I phoned they promise that it has been resolved and that the enquiry is now closed, but every month my account does not include the credit note/refund. I have spoken to call centre staff, managers and the managers' managers, but everyone is equally unhelpful and ***********.

ps. Vodacom Retention team also promised to send me a new sim card - but after 4 months this is also just an empty promise...