Xiaomi
Turn Call Waiting On or Off auf Xiaomi
Call waiting on a Xiaomi phone decides what happens when a second call arrives while you are already talking. With the feature on, MIUI plays a short tone and shows a pop-up, so you can accept, decline, or ignore the new call without dropping the current one.
Turn it off and any incoming call during an active conversation goes straight to a busy signal or voicemail on the caller's side, with no notification appearing on your screen.
On Dual SIM devices, MIUI treats each SIM as its own calling account. You need to check both accounts separately if you want the same behavior on both lines.
To change the setting: Tap on Phone ➔ Open the Menu ➔ Tap on Settings ➔ Tap on Calling accounts ➔ Tap on Call waiting ➔ Choose a SIM card (Dual SIM) ➔ Enable or disable Call waiting.
If the toggle looks greyed out, your carrier plan or the current network mode may not support call waiting on that SIM. In that case the setting will not react until you switch network mode or confirm the feature with your carrier.