This is, as far as I know, expected behavior. (I'm experiencing the same.)
"You can use test accounts to test an integration without affecting any real HubSpot data. Test accounts have access to Enterprise versions of the HubSpot Marketing, Sales, and Service Hubs, allowing you to test most HubSpot tools and APIs."
Actual calls are probably not possible as you could otherwise use a test account as a free Enterprise portal.
Best regards!
Karsten Köhler HubSpot Freelancer | RevOps & CRM Consultant | Community Hall of Famer
@karstenkoehler thanks. So, does that mean Hubspot calling feature is not available on the professional plan and it's only available on the enterprise sales plan? Can you please clarify? I'm trying to enable hubspot calling on my paid actual account and not trial account.