This may reveal my ignorance about smart phones - but I have the same issue with both Android and Apple, so perhaps it's something deeper...
I put several mp3 files into a box folder. I then access these through the box app on a phone. If I play one, the phone doesn't stop at the end, but goes on to play the next mp3 in the folder. This is not what I want. What can I do to prevent it, without putting each mp3 in its own separate folder? I can't find any setting to adjust.