Wrong amount debited for 3 months

Last year August i upgraded my data contract i have with Vodacom. The contract amount was R209 for 24 months, but to my surprise for 3 Months vodacom debited me R259 , I dont know why. To make it worse not a single person from vodacom called me regarding this.

On the 27 Of March i called Vodacom to esquire about this, the consultant gave me a reference number :1- ********** ********** and said they will call me back to sort it out, after a week no has bothered calling me. I even contacted them on their twitter paged they again promised to call me but nothing. i gave me my data contract number ********** 766 and the number they can contact me on ********** 715

This for me is *****, when a certain amount is advertised and different amount is debited, terrible service