Video calling is a Carrier Specific Feature. In order to use Video calling from your Natvie Phone app, the carrier must authorize the feature and allow it as a feature on your account with them. If they don't support the feature, a third party app would be required in order to make video calls.
Samsung should work will all carrier like they did when they standardized on the different names every carrier had for the Samsung Galaxy S product line because they wanted their own flavor. The infrastructure is there, they have to get beyond the politics, people want to use this app beyond individuals that might be on their Carrier network.
Thank you guys for your responses again, but I believe Samsung Cole got it. My S9+ Was under the Carrier of T-Mobile and my S10 plus is under the Carrier of Sprint. I was able on my S9+ to switch from audio calls to video calls. Video calls isn't even an option on my S10+ under my NEW Sprint Carrier for the this device. Thank you again.