I can't upload more that one playlist at a time. Every time I upload a different playlist, it replaces the existing one on my phone. I'm sure there's a way to have multiple playlists on my phone; but how?
Yes. According to the official FAQ website, you can sync multiple playlists at the same time using this application. You can view the steps to accomplish this on the site mentioned. If you can't solve your problem by following the instructions, you should try uninstalling the program and then install it again. This might fix your problem.