Oppo
Ringtone Volume Settings auf Oppo
On Oppo phones running ColorOS, ringtone volume and notification volume are controlled by two different sliders. Turning up one does not affect the other, which is why a loud notification tone does not guarantee a loud incoming call ring.
To change how loud your phone rings for calls, go to Tap on Settings ➔ Tap on Sound & vibration ➔ Set the Ringtone volume. Drag the slider to the level you want. The change applies immediately and stays in effect until you adjust it again or a Focus mode overrides it.
When this setting is not the fix
If calls stay silent even after raising the ringtone volume, check whether a Focus mode or Do Not Disturb schedule is active. These modes can mute calls regardless of the slider position, and they need to be turned off or adjusted separately.
Also note that ringtone volume only affects incoming calls. Alarms, media playback, and notification sounds each have their own volume control in the same Sound & vibration menu, so raising one will not fix a problem with another.