Frustrated with your poor service and communication!

I had a tracking device for my previous car with Netstar, so I traded the car end of September 2018 and told them to cancel the subscription since I no longer had the car, they told me the settle the account before they can cancel, which I then did, paid the outstanding balance and sent the proof of payment, no response from them then. And then today I got an invoice from them for R191.41 for April, mind you for a car I traded in 6 months ago already!!! I then called them to sort this but I was put through up to four people with the fourth one hanging up on me while I was waiting to be put through to the credit control department! I'm very unhappy that you are billing for a car I no longer have even after I have mentioned this to you so many times before, I will not pay this amount!