CoventryOne. Coventry One. Coventry Health Care Make up new policy and premium Sunrise Florida

I received a letter from ConventyOne August 27, 2014.  It clearly states my policy with them will end December 31, 2014, and it cannot be renewed.   It also states before my policy ends, I will get information about plan options available to me.

I contacted my insurance agent. We found a new policy with a different company that began on January 1, 2015.  Today I was checking my bank account and saw CoventryOne has drafted my account double what my "unrenewable policy" premium was.  

I contacted CoventryOne.  Their explanation is that they sent another letter to me on September 26, 2014 and the letter contained the plan they chose for me and the amount of my new premium. If I did not want the policy, I am to contact them to decline coverage.  I asked if they sent it certified?  Do they have proof I received the letter? The answer to both questions is no.

They say they will refund my money, but I have to provide proof that I am insured.  My argument is they terminated our policy with the letter they sent in August.  They have no right to issue a new policy or draft my account without permission or agreement from me.