Mix Telematics is harassing me please help ????

On valentine's day 2019 I received a call from Mix Telematics about a tracking device I told them I do have a tracking device already with Tracker SA the guy said yes we are doing an upgrade on their system and they've been trying to get hold of me since last year I said ok then they came to install the device after a day or two I didn't receive any email from the tracking company I've been using since 2017 Tracker SA, I suspected that something is wrong I gave them a call to ask about any upgrades they had they said there's no such thing. I decided to call Mix Telematics about the device and they should come unistall it cause the consultant **** to me that it was an upgrade from the tracker I'm currently using they told me I should pay cancelation fee, I said no cause that was not the agreement and till today I haven't received any T&C's or contract from this company. They are busy deducting money in my account when I told to come take their device. Please help me ????