Quick file Renamer doesnt work

Just spent 30 minutes trying to get this app to work. All I wanted to do was change the extension on about 15 files in a single directory. I went through the steps and the app told me that the extension was changed. But after checking in the finder, I found the extensions were not changed. I repeated this several times, same result. Limited, almost non-existent documentation, both online and on the support site. How do I get my money back?

JacobIsADrummer about Quick File Renamer