Samsung
Turn Call Waiting On or Off auf Samsung
Call waiting sits inside the Supplementary services menu on Samsung phones and controls what happens when a second caller tries to reach you during an active call.
When the feature is turned on, a short knocking tone plays in your ear and you get the choice to put the current call on hold and answer the new one. When it is off, the second caller hears a busy signal or gets sent straight to voicemail, depending on your carrier.
To change it, go to Phone ➤ Open the Menu ➤ Settings ➤ Supplementary services, then toggle Call waiting on or off.
This setting is stored on the carrier network, not only on the device. Some networks need an active signal or data connection to save the change, so if the toggle reverts on its own, try again with stable reception.
If calls go missing entirely rather than just the second call during a conversation, check Do Not Disturb or your blocked numbers list instead. Call waiting only affects behavior while a call is already in progress.