Xiaomi
Set Ringtone for Incoming Calls auf Xiaomi
The ringtone on a Xiaomi phone is controlled by a single default setting in MIUI. Every incoming call uses this sound unless an individual app, such as a video calling service, defines its own notification tone that overrides it.
On dual-SIM devices, each SIM card can carry a separate ringtone. If only one line plays the expected sound, the other SIM likely still points to the original default.
To change it, open Settings ➔ Sound & vibration ➔ Ringtone. On dual-SIM phones, pick the SIM card you want to adjust first. Then tap All ringtones to see the full sound library, including any tracks you have added yourself, and select the tone you want.
This setting only affects the built-in dialer. Apps with their own call or notification sound controls, such as messaging or video calling apps, need their internal settings adjusted separately if they keep playing a different tone.
If you only want to change the sound for messages or app alerts, that is a separate notification sound setting, not the ringtone. Mixing the two up is a common reason people think the ringtone change did not work.