Bad customer service from Vodacom

I upgraded my contract on the 5 June from a RedViP22 to a RedViP 50GB. At the end of July they deducted over R4300 from our account. Which was not the agreed amount. The agreed amount was R1890. Since the then I have been suffering to get this fixed. Now at the end of Aug they took 2100 off, which they should have not as I was due a credit. I have been up and down to the store in Riversquare and I cannot get it sorted out. Either Vodacom reverse this amount today or I will go to the bank and reverse it myself maybe then I will get someone to listen to me. I have been with Vodacom for 18 years and this is bad service. They are quick to take your money but not quick enough to recall their mistake. Hope someone senior at Vodacom can contact me today before I go over to drastic measures