za Xiaomi telefon...
Step 1: Dial * # * # 86583 # * # *. Once you are done, there will be a message ” VoLTE Carrier check was disabled ” appear on the screen, thus activating Volte on your Xiaomi phone
Step 2: Now go to Settings> SIM cards and mobile networks.
Step 3: Here you will have to activate the option Use VoLTE.
If your Xiaomi phone has dual SIMs, go to Settings> SIM cards and mobile networks> SIM1 / SIM2
After that, you can now start enjoying high-definition calls through 4G, LTE, or WiFi networks.