You do realize that these phones already have this functionality. Do not blame Samsung, blame your carrier. I can video call anyone on the T-Mobile network and MVNOs that lease the network. if your carrier doesn't have it turned on, that's on them.
Edit: Google Duo allows video calling anyone on any network in FHD video as well.
on Samsung's main dialer when you start typing in somebody's number you have the option to hit a button on the very left of the call button it looks like a little recorder that is The video call option sliquid is also correct that is a carrier function not Samsung's issue as well have had T-Mobile for over 12 years now and this has been a feature available from T-Mobile going as far back as maybe my Galaxy S3 so if your phone company doesn't offer that perhaps you need to make the suggestion there all Samsung does is provided the operating system and the theme that goes over it everything else is determined on what your phone provider wishes to provide to you
