CA trying to collect on medical bills

What is the name of your state? Alaska
in Dec of 2000 i was pregant and on medicaid I went into the hospital I did not have any stickers yet. Our hospital here bills from three seperate companies. Two of the companies are in the same building. The third is seperate. I had been getting monthly statements from all three. In July I had finaly recieved a retro letter to send to these companies that says that I was covered for the month of Dec. I did not send the letters certified but I did send them. I was in labor at the time and not thinking strait. I did not get a statement from anyone from that point on. I didn't get a phone call or anything either. Until June of 2002 when I was contacted by a CA stateing that I owed money to the hospital. Now I checked up and one of the companies had gotten the letter but the two companies in the same building did not get the letter. They only have a year after the date of service to bill medicaid. I talked to my case worker and he told me that they need to bill medicaid. But when I talked to the upper people in mediciad they said it would not be covered because I did not have proof that I sent the retro letter. My question is what are my options??? I started making payments because my husband and I just bought a house and we had to show that we were making payments. I really do not believe that this is my responcibilty. I work for a doctor and I know that when you bill medicaid that you receive less than if you bill that person. I am wondering if that is the reason they are trying to get the money from me instead of billing mediciad.