Cancellation of contract without informing the xonsumer

Ariva car rental are **********.I rented a car with them in December 2017 and paid all the necessary fees.We only had extra mileage in Dec holidays which we also made an arrangement to pay and it was confirmed. However without following their contract clause they sent the driver to collect the car without notifying me and my husband as per contract agreement. We used the car for 4 months and we were paying properly. After taking the car Ariva is requesting we pay the balance of the initial 60 months which is absurd. If anything they need to refund us. Why would I pay R110 000 for a car we used for 4 months and not owing any installment. These guys are ********** and I am taking them to the Ombudsman