Cell phone contract

I had a contract phone with them which I took over the telephone with their consultant about two years ago. It was a two year deal and I lost the phone in the space of 6 months then when I reported it to them they told me that I should've insured it and I was not advised by the consultant. But I continued paying for the device I didn't have. To my surprise the very same deal should've been finished 2 months ago and they still debiting my money, so I don't understand how they work please help me