Vodacom and their so called pro rata charges

I am very disgusted with Vodacom. I had a contract on my mother's name, which i paid for. So since my contract was due for an upgrade we decided to go ahead with the change of ownership. The only information I was provided with was that i should come in the first week of the new month and upon that I was "ONLY" going to pay an R150 change of ownership fee (to which I was fine with) Then all of a sudden I get my bill and instead of R358(the amount of my contract with a 2gig data plan) and the R150 ownership fee, that comes down to R508 in total, my bill is R579 for my first month that I need to pay for. I first went in to the vodacom shop where they logged the query. I almost waited the entire month to get feedback so I decided to contact the call center myself, I spoke to Marvin at the contact center and was first told that it is a pro-rata service I received from the 14 August 2018 up until the 1 September 2018, bearing in mind pro rata to me means you receive the specified data or part of it that you usually get every month, as this pro rata billing has happened to me before with mtn. I was also told by Marvin my bill is correct because I received a 1Gig pro rata data from vodacom on the 26th of August, which I proved to him I did not receive anything from vodacom it was a 1gig data I bought for R80 (and it also shows on my order history like that) Then I was asked to stay on the line to sort it out with solutions department. When he came back I was just told that the bill is correct, I tol dhim that I also have a recording system on my end and all of a sudden he wanted to explain how everything works and why my bill is the amount that it is, I kept telling him that I will not pay for something I did not receive, because I did not receive any data, the first time I received data was on the 1st of Septemeber, when I received my 2 gig data. How is it possible for Vodacom to just blatantly charge you pro rata when you didn't receive any pro rata from them and bearing in mind it does not even show pro rata on the invoice, which it should as it is "explained" as pro rata charges by their staff.