I have one contact (and only one so far) for which HubSpot always sets the country code to +44 (United Kingdom) when I attempt to phone the client, even though the contact is in the USA. This happens even when I explicitly set the country code to +1 for the USA.
This leaves me unable to contact the customer via the phone. I don’t know how it can be described as anything but a bug!
UPDATE: I formatted the number in the contact’s record as +1 (xxx) yyy-zzzz and the country code was not changed to +44 by HubSpot when I attempted to dial the contact.