Samsung MM-A900 / SPH-A900 / Ace

I recently transferred songs to my phone but didn't like the quality and deleted the songs; however, the phone is still saying that I have used 15.9 MBs. The thing is that I have NO file on my phone and before I transferred files, I had 47MB to use. I'm not sure why the phone says I still have used 15.9 MB and could not find in the phone where I could have used 15.9MB since I can't find any files. I was hoping someone could help me figure out why this is happening. Maybe a software problem? I have most updated software. Any ideas?