Bad service and Rip-off company

Tracker unit in my device stopped working and when i phoned tracker they told me i should bring in my car to a service centre at a a call-out fee of R550, i did not agree as i am the one who will be driving to the centre and the unit installed does not belong to me but tracker, in that case i was of the opinion thta let the owner of the unit take care of his unit and i will handle my monthly subscriptions as per our contract. After months of battles someone from head office finally phoned me to tell me they will not be charged a supposedly call-out fee and i should bring my car for a free repair. I was shocked when the said amount was debited in my next invoice. I plead with you to correct this else you will be in violation of our contract. i will remove your device and look for a new tracking company and wont be liable for any contractual costs. This matter is definitely going before the courts. I am also intending suing on grounds of doing business in bad faith.