What whos right?

Last week on Tuesday i was taken to my doctor for serious pains in my right side.He told me to go to the E.R.. I did they kept me over Tuesday night running tests, at first they found an infection but they ran more tests the next day on wedensday,i still wasn't released untill the next day.They found out that my gall bladder isn't working right and I will have to have surgery sometime later but anyways they kept me when i wanted to go home. So now my mom gets a letter from the insurance company saying they will not cover it because I wasn't kept in the hospital for any good enough reasons. My parents work hard but they do not have the money to pay for it. I was kept in the hospital by the doctors not by me or my parents for testing. So why shouldn't they cover it?I mean i could still have surgery any day because I'll need it sooner or later to remove my gall bladder.