Hi @ab,
The countries on that list are the countries we support calling to and from. So if a country is not listed in that article, you can’t make calls to phone numbers from that country. I would definitely recommend submitting Calling support for Slovenia phone numbers as an idea on our idea board!
I see you submitted a question about the Hubspot Sales Free product limits in a separate post, so those questions can be tackled there!
-Caitlin