Paying Twice

Anyone else tired of paying for songs twice? Sometimes I have to take off songs from device since there is the issue of space. Now I don’t have a computer to go through iTunes to get the songs back. There is a system that works some of the time. Find the album you bought the songs on. See that it says purchased, go to the song section find the song (make sure it’s the one from the same album and not a repackage or even under a different music genre the exact same one) click “the price” but sometimes you will get a pop up saying already purchased download for free? Which is great and all but sometimes it says purchased but it charges you again so it’s kind of like a gambling option