Xiaomi
Turn VoLTE On or Off auf Xiaomi
Xiaomi phones fall back to the 2G or 3G network for voice calls whenever the modem decides reception is safer there, even if a strong 4G signal is available. Voice over LTE (VoLTE) forces calls onto that LTE connection instead, which usually shortens call setup time, improves audio clarity and reduces battery drain during a call.
The switch lives inside the SIM management area of MIUI, separate from your general mobile data settings. Open Settings ➔ SIM cards & mobile networks, then choose the SIM card you want to configure if you run a dual SIM setup.
Inside that SIM's details, toggle Use VoLTE. Turning it on lets calls route over 4G whenever your network and plan support it. Turning it off returns the phone to older 2G/3G call handling, which can help in areas with weak or unstable LTE coverage.
Some carriers activate VoLTE only after a request, and a few SIM or plan combinations do not support it at all. If the Use VoLTE toggle is missing or greyed out, check with your carrier before assuming a settings problem on the phone itself.