Music from hard drive keeps deleting off iPhone 6S
I bought an old iPhone 6S to fill up with music I have from my portable hard drive to replace my old iPod touch. After loading a bunch of music I noticed after playing some songs the next day a bunch of albums will be missing. When I plug my phone to itunes the songs will be there but the deleted ones have the exclamation point and will not play. I keep loading the same songs/albums only for them to keep deleting. I don’t have wifi turned on, not signed into my apple id or apple music just bluetooth so I can listen. As far as I know the phone has the latest IOS 10.2.1. Can anyone help please?
Earlier iPhone models