First of all send a formal letter to your Ins. co requesting
an appeal and send it registered.

Second contact your government representative. They have people
who deal with these grievances.

Third, you can submit a request to an independent body for review.
Most states have these. Its simple and low cost. It takes power
away from the insurance companies and puts it in the hands of
"independent" and sometimes more importantly ..... medically
knowledgeable people.
See [link|http://www.deniedhealthclaim.com/insurance_appeal.htm| link]