Samsung
Allow or Mute Alarm and Notification Sounds During Calls auf Samsung
On Samsung phones, alarm and notification sounds are tied to a single call setting rather than separate controls for each sound type. When this option is off, every alarm and notification queues silently and only plays once the call ends. When it is on, alarms and notifications interrupt the call audio as soon as they arrive.
This behavior sits inside the phone app itself, not in the general sound settings, which is why changing volume levels or Do Not Disturb rules does not fix it. The relevant toggle is found under Tap on Phone ➔ Open the Menu ➔ Tap on Settings ➔ Tap on Call alerts and ringtone ➔ Enable or disable Allow alarm/notification sounds in calls.
Turning it off is useful if calls get interrupted by unrelated app alerts. Turning it on matters if you rely on alarms going off on time regardless of an ongoing call, for example for medication reminders or wake-up alarms during a call you cannot end quickly.
One side effect: with the option disabled, you will not hear any alarm during a long call, even one set for that exact time. It only fires once the call ends.