Schocking - lack of service from Vodacom!!!

Being a long time customer of Vadacom I am at this stage desperate for customer service and resolution to my disputes with Vodacom. In September last year I have upgraded one of my lines and signed a 24 month contract in store as per normal process. Since then Vodacom is billing me R400 more per month stating that their specials are different to their store's specials and no one is coming back to me with resolution. In February this year I have cancelled and paid in store the early cancellation fees - yet Vodacom continues to bill me the monthly premiums. I have been pushed from pillar to post - accounts department, cancellation department, the store, customer services, upgrades and retention department and all over again. I have multiple reference numbers for my disputes, and about R4000 in arrears according to Vodacom, which is the credit that they owe me. No one has contacted me for the resolution apart from sms's and e-mail letting me know that my account is in arrears - shocking! At this stage I would not recommend Vodacom to anyone and will cancel all my lines at my earliest convenience.