Was that text a positive compatible or not compatible?
Do a full power off restart of the phone. Then go in to mobile network settings to see if the toggle shows up. It might not. Go in to sim card status and look for IMS registered. It might not.
@Divit2 we don't have any feedback about people able to use S8+ with VoLTE on PM yet. But yes, S8 should have VoLTE. So, you will have to check the settings when you are in US
Worst case, try the voice in 2G and see if it works. Some people able to use 2G without problem.
and in case you cannot use voice with success, open a ticket with PM after and they usually would do something to compensate
Your VoLTE might or might not work in Canada yet, but should work in US if PM already enabled your VoLTE on your profile
before you go to US, enable VoLTE on your phone first
Ensure the Cellular Data switch is in the “on” position.
Tap Cellular Data Options.
Tap Voice & Data.
Ensure 4G or LTE is selected (has a checkmark)
At Settings, Select Connections-> Mobile Data->Enable VoLTE