A clinic can call a pet owner from Flow from three different locations:

The phone icon while in a chat

The "Phone Call" icon located in the client profile. 

The dialpad on the bottom right side menu.

💡 To record a phone call, make sure you select the "Record" button before starting the call

🚨Please note: When making voice calls on a mobile device, iPhone Flow users must stay on Safari and not use Chrome for successful calls