OnePlus
Assign a Custom Ringtone to a Contact auf OnePlus
By default, every incoming call on a OnePlus phone uses the same system ringtone, so you have to check the display to know who is calling. This behavior comes from the Contacts app, which lets you override the default sound for individual entries.
To assign a custom tone, open the Menüpfad: Open the Contacts app ➔ Choose a contact ➔ Open the menu ➔ Tap on Set ringtone ➔ Enable or disable Set ringtone for each SIM card ➔ Choose a SIM card (Dual SIM) ➔ Choose a ringtone.
On Dual SIM devices you decide whether the custom ringtone applies to one SIM only or both, which is useful if you keep separate numbers for work and private calls. You can pick a preinstalled tone or select an audio file such as an MP3 stored on the device.
This setting only changes the sound, not call handling. If your goal is to silence certain callers instead of identifying them, look at Do Not Disturb or Focus mode settings, since a custom ringtone still plays even when the phone is set to vibrate through some system profiles.