Voice over LTE lets you make clearer phone calls over our 4G (also known as LTE) network, where it's available. ​
How do I turn on VoLTE?

Here’s how to enable VoLTE on common devices:

Apple 4G device

Note: on 5G iPhones, VoLTE is enabled by default. These instructions are for 4G devices (iPhone 11 and earlier). 

1. Go to Settings
2. Go to Mobile
3. Go to Mobile Data options
4. Go to Voice and Data
5. Tap 4G and toggle VoLTE on ​

Samsung

1. Go to Settings
2. Go to Connections
3. Go to Mobile Networks
4. Toggle VoLTE on ​

Google 

1. Go to Settings 
2. Go to Network and internet 
3. Go to Internet 
4. Go to Settings (next to SIM) 
5. Toggle VoLTE on 

If you don’t have one of these devices, check your user guide.