Incorreclty billed and false advertising

I took a 24-month contract with Cell C late last year and it was done over the phone. I did not go to any Cell C store they called me and offered me a deal of 2 cellphones a Samsung A34 5g & Samsung A24 , when I checked the deal it was good. I then asked the sales what is the lenth of the conttract and how much I'm going to pay monthly I was advised that it's going to be R 499.00 , I also asked her there are no hidden cost and I was advised there are no hidden cost. The first month I paid my monthly installment with the pro rata which I didn't have a problem with . The problem started when they started deducting R 509.00 instead of the R 499.00 which I agreed upon , I also thoght it was a mistake that will be corrected and it was neveer corrected. November last year I called their customer care and requested a copy of myy contract and i was never issued with. I then called them today to query my installment , firstly I was sent from pillar to post ( from 1 department to another) then finally spoke to on eof the agent and we ended up arguing with her, she said to me I'm paying my installment and 15% vat. I asked her as to why I was not advised about the 15% vat , she said it was a miscommunication and no one is at fault. I was shocked and asked t speak to the line manager and she put me on hold and hung the call. The contract that i took it was for R499.00 not R 509.00 , I would like cell c to rectify this and refund me back my money and furnish me with a copy of my contract.