The Hospital Is Trying To Collect Money Already Paid.?

I will go briefly over the situation… I went into the hospital a couple of time in a month due to an illness. My insurance was just getting started and the date was just prior to my entering in the ER. I didn’t even know I was covered yet. At the end of that month I gt a letter saying I was covered.
Then I had to send the hospital my insurance info. for them to collect the monies. At first the Ins. Co. did turn it down saying it was a preexisting condition… but it wasn’t. After I spoke to them, they saw they were wrong and agreed to pay all except the co-pay. They sent me the statements (EOBs) and when I spoke to the hospital financial dept they wanted copies of them to prove it had been paid. So I did fax it over. They still didn’t get it. Then I sent it by mail to the head manager. They didn’t get it. So he asked me to fax it again. So I did just about ten days ago.
Today, I get a call saying they didn’t ever receive anything and are getting ready to take me to court. I’m real upset.
Can you tell me what I need to do. I have called all the people who I owe money and they say it’s been paid but they are the their financial collection company and insist that it does show payment.
Please I really appriciate any help you can offer. Thank you.