Samsung M520 Owner's Manual page 199

Press the Right navigation key to play the next song in your
playlist.
Press
Note: The first time you access one of your Available Channels, you are
prompted to accept the its monthly fee (unless it's a channel that
doesn't have an associated monthly fee). Accepting the charge gives
you access to the channel for as long as you continue to pay the
monthly fee. If you accept the fee, the next time you access your
phone's media player, this channel will appear in your My Channels
section.
Section 2J: Using Your Phone's Built-in Media Player
to play or pause the current song.
173