Vodacom Fibre Robbing me

I have been on Vodacom Fibre for 2 years now, it was a 10Mb line, I then got a invoice last month for a 50Mb line, I received no communication about this, and this large amount was just debited, i called them to find out about this, and asked them where the communication to me was, and they did not get back to me. I have been testing my speeds after the talking them, and i do not get more the 5mb download and upload speed for the past month now. They Are ridiculous ! i am still waiting for a call back after logging this issue a month ago!!!!