TOTALLY MISLED

I have a SKYTRAX unit installed in my vehicle where I can log onto the Tracker website which gives me all the flexibility of viewing and tracking my vehicle online. There are options on the website where I can modify certain settings and add notifications to see where my vehicle goes. I had believed that this was all part of the package It was only until yesterday when I received an SMS to say that I owed Tracker R2500 odd rand. When I called to follow up they told me that this was for the SMS notification costs on the vehicle. I am surprised, why didn't they send me an account before so I could see that I have been charged for this each time, months have gone by and sometimes I get the same SMS repeatedly sent to me. I don't think that it is fair for me to pay for this for surely if I knew that there was a cost involved I would not have set this up. I am only prepared to pay the costs for the first month of using this service. HELP! I have 2 Tracker units installed in vehicles at the moment.