Worst Billing and useless tracking company

This is the worst tracking company EVER!. Firstly I contacted them wanting to install a unit for my new car. They didn't tell me that the unit is not recognised by insurance companies. Had to rebook again to get another replacement unit. They advised me that I must go through my insurance which I did. Months later they send an sms saying my insurance has stopped paying them and I should pay directly to them R148pm via debit order. At first I was OK with that. Come debit order time they debit R408! It bounces from my account. Then they are now threatening blacklisting me and all of a sudden they say I must pay R682! How in the world do we jump from R148 to R408 then R682 in less than a month????????? And without prior notice!