OnePlus
Change the Ringtone auf OnePlus
OnePlus phones ship with one shared ringtone for both SIM slots by default. That works fine for single-SIM use, but Dual SIM owners often want a distinct sound per line so they can tell at a glance which number is calling before they even look at the screen.
This setting lives inside the sound management module of OxygenOS, not inside the SIM manager. That is why many users check the SIM settings first and never find the option there.
To set it up: Open the Settings ➔ Tap on Sounds & vibration ➔ Tap on Phone ringtone and vibration ➔ Enable or disable Set ringtone for each SIM card (Dual SIM) ➔ Choose SIM card 1 / 2 ➔ Choose a ringtone.
Enabling per-SIM ringtones only changes the call sound assignment. It does not touch vibration patterns or message notification tones, those are configured separately in the same sound section. If you only run one SIM card, skip the toggle and pick a single ringtone directly from that menu instead.
Custom audio files already stored on the device also show up in the ringtone picker, so you are not limited to the preinstalled tones. If a ringtone reverts to the default after a system update, the sound profile was likely reset, and repeating the steps above fixes it.