Vodacom customer services total incompetence

Vodacom has overcharged me by R200 per month for more than 24 months. During this time I had to log repeated queries and go to the branch. The vodacom branch manager at Paarl Mall admits they are at fault and copied me on a mail to customer services where he explains to them their fault. Eventually, after numerous more follow ups, the branch manager informed me that Vodacom admits the mistake and will credit me but that he cannot say when. After a couple of months I started following up again query after query and after a few weeks Vodacom informed me they will not credit me. My experience with the branch is good, but even the branch cannot override the incompetence of the group / customer services. I have since moved to MTN but I am still owed the money by Vodacom.