Ridiculously expensive Internet

Initially I was very impressed by the service I received when taking out my 10G Vodacom LTE contract at Hatfield Plaza. But the excitement subsided very quickly after the amount of R3267.98 was debited at the end of June, so I went back. Marthin explained that it was due to the fact that I was only awarded PRO-RATA data for the Month of May, and the high amount was because I went over the pro-rata cap. I can't recall that he mentioned the pro-rata situation AT ALL, why would I then go and download loads of stuff knowing that?! I requested that he put a cap on my account and also requested that I receive statements via e-mail. I also phoned him the next day to find out what my usage was for June, and he confirmed that I went over my cap with a few megabytes. BUT YET AGAIN another exorbitant amount of R3251.20 went off. The Vodacom data disappears into thin air. I used to use Telkom data, which went much slower. I DON'T WANT THIS CONTRACT ANYMORE! As I have been with Vodacom with my cell number *** over 10 years now, I believe that you guys can help me get out of this ****. I was not advised correctly and this internet is costing me a fortune every month!!!