Horrible experience with MiX Telematics call centre

Hi please advise because I have never come across with such a mess of a customer service ... I am not sure if this company gives training to their staff this is very disappointing actually I am disgusted... I recently found out that my email address was changed on their mailing list to the previous owner of my car. Apparently she also had an account with them and they used her email request to change details on my account even though she had an account of her own. I requested for the cancellation email to be send to me, they forwarded me the email with the previous owners full details, her home address, cellphone, work email the works, which I think as very irresponsible. For the past 3 months I have not been receiving any communication from them. I am now not covered because of an invoice that I have never received and was never even called to advice me that my account is in arrears. The invoice that I am apparently in arrears for is for a call out that we were advised there would be no charge for it. We have been in contact with them for the voice recording of that call we are still waiting for them to respond, we decided to call them again today and we were taken from pillar to post. Mary does not know what Martha is doing and we are now getting very frustrated. I requested for a cancellation in March already, I am still being debited for that car and the car was sold. They debit my account monthly, but for some reason, they don't run the debit order for the roadside assistance invoice, and I am not covered currently because of their incompetence. Does it make a sense if they debit us for tracking system and they are not willing to respond to alarm because of arrears for road side assistance that was never communicated. This is the worst thing we've ever experienced with a tracking company..now I am looking for a better tracking company if they don't change the way they treat their customers. They don't take responsibility, they never apologised, they never followed up on my queries I am the one who has to call them.