I'm not positive, but i think they charge an astronomical amount for calls that don't originate from a local calling prefix. Of course you can get those, but some countries require ID.

Mainly I know that calling from a voip number was really expensive when I tried to set something up for a family member going on vacation to Europe. That probably cuts back on a lot of spam calls.

I don't know how it is with companies, but there are countries where you can have subscriptions which allows you to call any EU numbers without a surcharge. And what I saw weren't even that expensive, around 50 euros/month.

It may be less bad than some of the stories I heard from the US but it's still enough to never pick up the phone unless you're expecting a call.