It is controlled by the carrier and metro pcs does not allow this feature I switched to Xfinity mobile and they finally enabled it on their galaxy phones but it is up to the carrier to enable this feature one of the reasons I switched to Xfinity
I have been struggling with this and thought people might benefit from my experience.
I got an "unlocked" S10 (meaning directly from Samsung.com and non branded) and I was with At&t carrier.
I tried and wasted so much time talking to different At&t and Samsung people and there is simply no solution to activate the WiFi calling.
I went to T-mobile and the minute they put their sim card in WiFi calling was up and running.
It is sad that you have to switch carriers for this but if you have no service at work like me, WiFi calling is essential.
Hope this helps.
All Samsung phones, regardless of carrier, ARE able to utilize all features regardless of carrier, they all have the same features, However, the ability to turn them on or activate those features are dependent on some configurations that Sadly, general users do not know, and are potentially hidden from.
There are some public write ups on how to turn on all of these features, but it takes some work.
We configure these things for customers all the time. It certainly is sad that the carriers play these games and limit their customers, and use them as ploys to get your business.
Hope this info is promising for everyone who reads this reply.
Google is your friend on this venture to enable all your available options. Good Luck.