Continues billing after contract expired

I took Netstar through my previous insurance and I was told it’s a 3 year contract. Netstar made me aware that if I cancel with the insurance with in the 3 years they would debit my account directly . I canceled with the insurance after 4 years and Netstar continues trying to debit my account and even handed my account over to their collections department. I called to enquiry and I was told it automatically becomes a month to month contract after the 3 years of which Netstar failed to disclose on the documents I was sent when I originally joined .