Billed for a cancelled tracker for 4 & 1/2 years!

I am extremely disappointed in the service that I am receiving from this company.

Somebody in their sales department called me to arrange for an upgrade to my tracker, as it is older than 3 yrs. I called into Netstar myself to verify if this sales call was legit as I have had this specific tracker for more than 4 years already. Whilst the consultant assured me that I can trust the sales department, something else came to light on my profile:

I have been deducted for the last 4+ years for a prior car tracker, which was cancelled in 2021. This specific car is what I have traded in at the time that I purchased my current vehicle. Since then, I have called in a few times, with the call keep being cut off, holding for as long as 24 minutes at a time. It has been more than 3 weeks now. Each time I need to repeat my story to the consultant, only for them to either transfer me to the Retentions or the Cancellations department. I have also been transferred to Netstar Telesure, who are not getting back to me. The registration number on their system for the current car is a personalised plate, which matches the registration number for the previous vehicle. How is this possible that this was not picked up? When communicating my increase for monthly instalments, the letters sent to me from Netstar indicate the registration number of the car and not the identity of the car. How do they conduct thorough tracking?

In addition, if they thought I still had this car in my possession, why not call me and offer an upgrade for a tracker that is obviously older than 3 years, at the time?

This is not good customer service and makes me not have faith in the fact that I have 2 other trackers currently fitted with this company.

In the interim, the sales department is also no longer calling me to offer that upgrade to the tracker, so all I see is inconsistency with how their things are managed from their side.

They have also said they are investigating this with my insurance company as the tracker was installed via my contract, at the time, with Dial Direct. At this stage, I was still billed for this tracker last week, which I cancelled with Netstar last month. I am not trusting these people, at present.