What a poor service!!!

This is the worst company I've ever worked with, I reported that I couldn't pickup my car location on the app and when I check the recordings for the routes I have travelled, I couldn't pickup the records for over a month which mean the device wasn't working for over a month. I called them to verify this and they told me that the device was faulty and it was out of warranty. but this was not communicated with me. They said I need to pay R600 to have it fixed. I wasn't happy about that, so I cancelled my account with them. They have a very poor system in managing their clients but excellent system for debit order collections, because as soon as I reversed the debit order for that month the following day they called to request a debit order. Now I'm receiving calls at least four times a day harassing me about that reversal, they expect me to pay for the service which wasn't rendered. I am tired of these calls, every time I have to explain myself. this is harassment now. If my car was ****** they said they wouldn't have able to find it. So what service are they rendering.