Insurance question. Newbie

[DBarringer58 0]

I have done all the test and been on a medically monitored diet since June 2015 from my GP. I get a call today from the bacrectic Dr. Insurance lady confirming that Medicare approve my surgery and she tried to verify it was my primary insurance. I told her no that my husbands ins. Was the primary and Medicare was secondary. And I told her( like I did in Oct ) that my husband's insurance would not approve it. She said I was on the cancellation list and they had a cancellation on the 27 of this month. I told her I wanted it but she said she would have to speak with another lady about the insurance. I am now very concerned . Can they denie me. I thought if my husbands insurance. Denied it Medicare would pay the 80% and I am responsible for the rest. Which I am prepared to pay. Any help with this is greatly appreciated. I am really upset over this! Thank you so much