Over charged and to verify if my tracker is working

I have agreed to pay R199 per month and as I had six days before pay day, i was told that i will be charged R6 per day until my pay day. An amount of R136 was deducted from my account by cartrack. I am so afraid to see how much will they deduct on my pay day as I heard many stories after agreeing to their offer. I am not even sure that my tracker is working, I have tried to use their app but it does not show where my car is.