Incorrect billing on my account

I had a contract with Ctrack on my opel corsa in 2012, I asked ctrack to come remove their unit in 2013 which they came and remove it until i bought a new car in 2014 and asked them to install my old unit to my car, the sales person said to me he will upgrade my unit and give me a new contract but cancel the old contract<br> <br> but i've noticed everymonth i was charged for 2 units and i called ctrack to help me resolve the issue which they asked me to send them an email which i did, after they said they will try to resolve this issue, time went pass and someone from ctrack called me and said they are still busy with my problem, since then they never called me or send me an sms saying my account is in arrears or anything until they deactivated my account, then i called them to find out what is wrong with my device they told me i was handed over to debt collectors while i was still waiting for them to correct the billing issue.<br> <br> I've never recieved an sms from them saying i owe anything on my account, now they are saying i need to pay 15 000 rand and my contract doesn't even cost that much.<br> <br> I've bn with ctrack for many years, i've never experiance such a bad service, I hate ctrack