******* with replacement Tracker contract

I called Tracker's Call centre on 17th January 2020 to give notice on the add on service on my Tracker account. I explained to the agent that, as I am a pensioner, I could no longer afford the add on. I was persuaded by the call centre agent to take a 'new and improved package' with a new Tracker unit and sign up for a new contract, which was cheaper than the one I had and he assured me that I would only be paying for the new unit as from 1 February. He never mentioned anything about notice on the existing unit, with one contract simply seamlessly replacing the other. I received an invoice for my new monthly amount and was advised that their would be pro rata amount for January, with which I was completely happy. Much to my horror, I was debited on the 1st for my new installment as well as my old installment for a Tracker which I no longer have. I called the call centre this morning and was advised that they wouldn't refund me as I had to give a months' notice on my old Tracker. Had I know that I would have to pay the notice month, I would have kept my old unit during the notice period and had the new unit installed on the 18th of February. Why did he not explain that to me? They couldn’t get here fast enough to install the new unit and now I see why!! Why would I pay for something that I no longer have??? The agent grossly misrepresented the facts to me for the sake of a quick sale. They had no right to deduct this money from my account. How do I know that I’m not going to have a repeat performance of this at the end of this month? They are authorised to deduct only the amount of my current’s month’s invoice which I received by email and which was correct. Had I received an invoice for the amount deducted, I would have immediately queried it and the money would never have left my account. I still do not have a breakdown of the amounts deducted. If this issue is not sorted immediately, I have every intention of cancelling my new contract and referring this matter to the Ombudsman. I AM TOTALLY UNIMPRESSED WITH TRACKER!