<human>: Can you give me the gist of the text in a nutshell?

Hi all, I live in Atlanta, GA and I went to the hospital in Fall 2014. One of the bills I received from the hospital was $120. I had no idea about this bill (they were supposedly sending me mail that I never received), but my dad happened to receive one of the bill notices at his address in a different city and paid it off without telling me. One day at my current address, I found out about the bill by receiving a collections notice about it, so in my confusion I immediately paid for it. After mentioning it to my dad, we realized that there was a double payment (one directly to the hospital and the other to the collections agency). Since February of last year, I've been periodically calling the hospital trying to get my money back and having them inevitably tell me the process takes 6 months. It's been over a year and they told me they were sending me a check in January this year. However, end of January I received a bill TELLING ME TO PAY THEM $120. Of course I call about this and they say they're sorting it out. Today, they sent me a "Past Due" notice for the same amount saying that they will transfer me to collections if I don't pay. I must have called they're billing and accounting department at least 30 times in the last year (and been there in person at least twice). What the heck do I do about this?
<bot>: Accidentally double paid a hospital bill a year ago and now they're sending me bills to pay them for the amount they owe me.