Wrong invoice amount

Good day team

I am sitting with a big problem at the moment. I have a contract with Vodacom of R202 monthly. My latest invoice came with a due amount for this month of R500.01. I called the customer care department 2 times and was told that instead of purchasing once off data on the 1st of November 2018 a selected the option recurring data which allowed Vodacom to credit my phone an additional 1 Gig for the month of November and apparently December. Secondly the amount that I always buy for is R149 which is 2Gig data 1 Gig day and 1 Gig night. Thirdly I have all the proof on my phone since I took out this contract early this year and at clearly states I bough once off Data and not recurring Data as I always make double sure when buying data. Lastly I check my balance regularly and never came across having more data on my phone as to the amount I normally buy. I explain all of this to them, they logged a service request to go through my phone and still told me I selected recurring and not once off. I think they are trying to rip me off and expect me to pay for what I have not received. The invoice states 1 Gig recurring data of R129.57 for November and also for December same amount. I never received any additional data and my sms's won't lie to me. I refuse to pay this amount and will only pay the amount of R202 which is my normal monthly installment. Please Vodacom, short this mess out as soon as possible.