Copyright infringement on an original piece????

I have recently received copyright notices for a few of my pieces, which is understandable seeing as they are arrangements (Although it is a bit suspicious how many were copy righted in such a short amount of time). But, what I don't understand is when I received a copyright infringement on a completely original song that I composed. I filed a dispute but it hasn't been answered. Who reviews the disputes, how can I ensure that whoever does sees mine, and why was my piece claimed against?