Open Question: Hospital Billing Question - Doubled Amount After found out had Insurance?

My Daughter had to visit the E/R on Spring Break - we received a bill for $295.00 as the adjusted amount due - assumed she had no insurance. I faxed her insurance information and it was filed. It was all applied to the deductible now the hospital wants us to pay $581+. How can they double the bill because she had insurance and it did not pay? If the first amount would settle the bill how