Mobile Talk are ****** and they sales agents are very rude on the phone

I resently took a WiFi Router with Mobile Talk. The agreement was that I pay R119 & I get 10 gig of Data. At first when I open my my router there was 2 Sim cards I did not know what to do with, so I opened 1 used it. The other one is still closed. To my supprised now I received an invoice from Telkom showing that I owe the amount of R496. This is not what I signed up for. Mobile Talk are ****** and I'm definitely blocking them from taking money in my account