How to solve Redmi K40' s disconnection when answering the phone? thank you

If you don't turn on the VoLTE service when you make a phone call, the mobile phone network will automatically fall back to 2G or 3G, and you can't connect to the network during the call.

Therefore, if you want the mobile phone to use the network normally during the call, you can click the corresponding SIM card in Settings-Dual Card and Mobile Network to start the VoLTE service. After successful opening, a high-definition logo will appear next to the signal icon.

If you use two SIM cards, and you want one SIM card to be able to access the Internet during a call, please turn on the VoLTE function of the two SIM cards, and turn on the option of "Connect to the Internet when the secondary card VoLTE calls" in Settings-Dual Card and Mobile Network.