GaryB82 that is not an option. You can not video call straight from the phone app provided by Samsung. You must download a 3rd party app for video calls. Some exceptions on your part may apply.
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.
I have an unlocked Galaxy Note 10 Plus, bought directly from Samsung. I called Verizon, they indicated that the feature is part of the firmware and is not something that they can enable on their end. Native video calling between Samsung devices simply is not available unless both are from carriers that support the feature. I haven't called Samsung directly but will do so as one last effort.
I am a diehard Samsung user. With that being said, this ticked me off. The problem is that the option is not offered on unlocked phones even though they are carrier specific. I got my T-mobile S10+ on pre-order from Best Buy. It's a T-mobile phone with all the T-mobile stuff. But because it's not "from T-mobile", the video call option is not available. Stupid! Yes I use Duo now, but I recently got 8 coworkers to switch from I-Phoneys to Note 10+ (various carriers) and was trying to show them how these phones have the same facetime feature. How stupid I looked when I didn't have the capability when they did. Samsung, we expect more! You already removed the dual photo feature, the headphone jack, and now this. LG and Pixel are looking pretty good now.
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.