Select an option from Settings > Sounds & Haptics > Ringtone to set a new default ringtone. You can use a third-party app to create a custom ringtone. Select it as the default in the Ringtone settings ...

You can change your ringtone on an Android device to a preset or custom tone, all through the Settings app.

When you press one of the volume buttons on your iPhone, you'll notice that it changes both the media volume and the ringtone ...