WhatsApp is one of the most popular messaging apps ever. It's one of only a few that can boast over one billion active users. It started out as a text chat service before Facebook bought them a while ago. Since then, the app has integrated voice calling, video calling, and tons of other features. The video calling works quite well and you shouldn't have any problems using it. Not everyone trusts the app since it's run by Facebook. However, if you're just looking for something that works and is stable, this is a good app to try.
Signal Private Messenger is one of the most popular privacy chat apps. It features end-to-end encryption for all messages, voice calls, and video chats between two Signal users. It focuses a lot on individual chats. There are group chat features, but it's mostly for personal use. This is one of the biggest differences between it and rival privacy chat app Telegram. Video calls worked fine in our testing so we have no trouble recommending them. It's a neat way to get some encrypted chats as well. The app is also completely free and open source. You can't really go wrong with it, but there are better video chat apps if you need group video chats.