This is how I changed ringtone in M30s. Open settings, sounds and vibration, ringtone, sim 1( I am using 1 sim only), choose ringtone. If not happy with ringtones present, tap +sign at top right corner, it will open audio files on your phone. Select one you like and decide if you want whole song or only highlights. I chose highlights only. It will now be seen in the ringtone selection. New Ringtone will be set.
