Ringtones won't play!

I had to purchase my 6 ringtones again after upgrading to iphone5 and now none of the ringtones are playing as they were assigned to contacts. I've tried everything and Marimba keeps playing and it is not even selected as my default tone. I've seen many similar issues posted on the web and tried them all, but nothing works permanently. The tones rang in okay for a couple of days and then they were gone. Why aren't there simple instructions on how to set this up and which boxes to check on itunes for synching tones, etc. 'm totally frustrated and disappointed with Apple. Life was much simpler with my Android.