Hello @GeekBone
LTE works fine on compatible devices, which means that if your device has an LTE modem and your service provider has coverage, you can use the data connection leveraging 4G.
Regarding VoLTE, it has been reported some successful experimentation on specific devices.
At this stage, if you're not involved in the development of Ubuntu Touch, it is not possible for you to use VoLTE on any device.
Plus, those results were made with 24.04 (Noble), so basically VoLTE won't be available for Focal and further less for Xenial.
And there is also some further work to get done until VoLTE is ready and available on some selected devices.
Progress has been done, encouraging work is still in motion, but it is not ready yet.
VoLTE is a feature that won't be available on all devices, so it will probably appear on the device page and it will fall on the maintainer(s) of a port to enable it. Currently there is hope that the work done can be more or less replicated on other devices sharing similar SoC, but it needs to be proven as sometimes manufacturer do strange things when logic dictates they should have done things the same way...
I hope this clarifies things a little and also hope I didn't betray the amazing work done/in progress to bring VoLTE to our community.