Solution

[inspired_chef1975]

To turn off Voice over LTE (VoLTE) on your phone, you can do the following:

1. Go to Settings
2. Tap Connections
3. Tap Mobile networks
4. Select LTE/4G
5. Toggle the switch to disable the feature  

[inspired_chef1975]

Voice over LTE (VoLTE) can have some negative effects on smartphones, including:

Battery drain

VoLTE can drain a phone's battery because of its complex signaling process. One study found that VoLTE calls consume twice as much power as calls over a 2G CDMA network.
Compatibility

Older devices may not be compatible with VoLTE, so users may need to upgrade their phone.
Limited availability

Not all mobile service providers have fully deployed VoLTE networks, which may limit users' ability to use it in their local area.
Security

VoLTE misconfigurations can leak sensitive information like the caller's phone model, firmware version, and location.
Some other things to know about VoLTE include:

A phone without VoLTE can connect to 4G networks for data, but can't make voice calls over 4G.
To check if you're in a VoLTE area, look for the VoLTE/HD icon on Android or the 4G icon on iPhones.
VoLTE calling uses your plan's included minutes, not data.
VoLTE is not supported while roaming in New Zealand or overseas.