Tracking unit

Cartrack was great until I had to change a vehicle unit from one vehicle to another. There was an agreement that there was a fee that I had to pay of R870.00 and I honoured the payment, however I am being threatened with legal actions because there was another fee of R600.00 that had to be paid. I've been requesting for telephonic recording for almost 2 months now, where I spoke to one of the consultants who told me that because I am removing a unit from 1 vehicle to another there will be no costs. I am receiving countless emails that my account is in arrears, now they are telling me to make arrangements to pay that amount over 2 months with my subscription amount or my services will be suspended, and I won't access to the app, vehicle positioning nor receive notifications regarding my vehicle. I am not happy about this at all.