Calls are currently in beta. To start using this feature, you'll need to enable it in your settings. Here's how:
Mobile (iOS and Android)
1. Open Settings
2. Tap on "Privacy"
3. Toggle on "Voice and Video Calls"
Desktop
1. Open Settings
2. Navigate to "Permissions"
3. Toggle on "Voice and Video Calls (Beta)"
If you want to learn more about calls, check out this video: