Vodacom ******** its customer

I upgraded my contract to Smart XL package (R736 including Handset with no extension of the contract) after receiving a sales call from Jakia who is working for Vodacom on 23 Mar. (although, I'm not sure if this is the accurate spelling of her name). She confirmed serveral times the final price and the condition of the package and said there was no hidden "fine print" on this offer. However, on 10 Apr, I was suddently charged R1245 for Smart XL + Handset. I called the Vodacom customer service numerous times (Apr 13, 17, 20, 24, 25) with no avail. On 25Apr, Verona from Vodacom called me to confirm that my subscription would go back to the original package from 01May. I asked about April Invoice which was overcharged but she said the management would check it. Since then they never got back to me nor changed my subscription back to the original package. Basically Vodacom ******* me into this contract, not returning my call or doing anything to fix this situation.