Double billed by Vodacom

I requested that Vodacom no longer debit my cellphone contract account as I would prefer to pay cash each month because they would incorrectly debit my account with additional amounts that i did not know about!! I would call and they would never help me. This month I paid R400 in cash (which is my contract amount) but they still debited R645 after i had paid!!! Not only double billing me but also adding R245 which i know nothing about! The same thing that has been happening all year! When i call i get given the run around, they promised to pay thw money in 2days but those two days have passed and nothing! When i called again today i was told that the accounts department is closed and now I'd have to wait 14-21days for my money to be repaid!! This is appauling service from Vodacom after months of being incorrectly billed i have to deal with this now!! Each consultant tells me something different! The reference number i got is s390g2q-qlnlv. I'm fed up with the service I've recieved since i got this contract!!