garne2t -- I found this out the hard way, too! I pushed the issue really hard for several months with a new, unlocked Moto G7 that is wifi calling capable. After a few days, it just became a matter of principle for me and I spent way, way too much time reseaching this.
Motorola tech support finally admitted that unlocked phones are considered to be a pain in the butt because of a variety of issues that really boil down to money. Unlocked phones are the very, very last to get updates -- the carriers will complain if they don't get the updates quickly and they generate oodles & oodles of money for the manufacturers. Do you really think Samsung or Motorola cares if my or your unlocked phone isn't updated in a timely manner? No, of course not -- we have no financial impact and they don't make hardly any money off from unlocked phones, but make millions off from carrier phones. The carriers get the updates first and then the unlocked phones are almost an after thought.
The phone manufacturers offer the advantage of a fairly clean version of Android with an unlocked, non-carrier phone, but it comes at a non-monetary cost. In all that bloatware that the carriers add, there is actually some useful and very necessary software that enables features such as wifi calling and video calling. Without that bloatware, there is no wifi calling because it cannot be enabled as there's no software on the phone to enable it. And, as I discovered, you can't simply install the bloatware - the carriers won't do it for good reasons (they could brick your phone if you goofed around with it and then no one would be happy!). I got into a long back & forth with Motorola tech support and Verizon tech support -- Motorola kept telling me that Verizon needs to provision wifi calling on my account. Verizon kept telling me that it was provisioned but my phone wasn't capable -- of course it was capable, but didn't have the Verizon software so the phone could communicate with Verizon, which was discovered once Verizon tech support escalated the issue. At that point, it was end of story.
I actually had a Samsung Galaxy S8+ that is in good condition and I've gone back to using that as it is a Verizon phone -- and I have all sorts of features that I didn't have with the Moto G7. My S8+ has a slight crack that is only visible at an angle, which drove me crazy at times and I thought a Moto G7 would be a step up... not even close for a lot of reasons, but the lack of wifi calling sealed it.
The kicker is that even though I researched this before I bought the Moto G7, I saw what I wanted to see to a certain extent and ignored some other stuff. Hindsight is always perfect, but I was a bit foolish for dropping $300 on a new Moto G7 that is inferior (in many ways, not just wifi calling) to my "old" Galaxy S8+ -- but, that seems to be human nature and it's easy to blame Verizon or Samsung or Motorola or whoever!! Bottom line for me is that I am going to lose money on this stupidy (I'm trying to sell my Moto G7 on ebay - I'll be lucky to get half of what I paid - but this was totally my fault. Huh, look at that... a little personal responsibility, that's not something you see often!