Usually Samsung phones directly supplied by Samsung are Unlocked to all network's @Sanzantro
What you need to probably remove is the Region Lock which is carried out by making a culmitive call of 10 minutes in the country of origin using a local sim card and the call is made to a local number.
That or it's been known for the Samsung support Department of that country to be able to remotely remove the Region Lock.
Regarding voLTE.
This is driven by the networks sim card and firmware on it.
For example in the UK if a person is on Vodafone UK then the phone has to have been bought from them for voLTE to work due to the type firmware on it.
The iPhone being the exception.
You would need to check with your own networks support faqs for voLTE and perhaps speak to your networks customer services.
Also other features like Samsung Pay may not work.
Also look at the Terms and Conditions of your Manufacturing Warranty to see if you'll be supported if you ever need assistance from Samsung.
Daily Driver > Samsung Galaxy s²² Ultra 256Gb in Phantom Black.
The advice I offer is my own and does not represent Samsung’s position.
I'm here to help. " This is the way. "
