What should I do about my music on my IPhone?

I downloaded music off of the music app (which is ITunes) on my iPhone 4s, and when I go to my playlist, all of the songs I bought are there, but when I go to play one. It either doesn't play, or skips to A song that does play. Then when I go back to the app from my phone, and type in the soundtrack and/or songs that don't work, some say I bought them, and others it says I didn't. I bought 34 songs and only 3 actually play. Can anyone help and give advise on what to do? (I also bought the songs a couple of days ago, so they have had time to finish downloading)

Reboot your iPhone by holding the home and lock button until it closes and reopened.

This happened to my iPod once, and when reboot didn't work, I just deleted all songs and downloaded them back from the iTunes Store under "Purchases" and then "Music".

If they still don't work you may have to ask the experts at Apple.