They're making you ring them?! That's ridiculous! Personally I would just flat out refuse, there is absolutely no excuse for them to put the cost on you unless they can't afford to hire you anyway.

In the US you're generally charged for every minute of a call on the phone regardless of whether it was incoming or outgoing. Most postpaid plans now include unlimited minutes, but prepaid are limited.

I believe European carriers were traditionally caller pays, not sure if that's still the case.

No, they call me, but I get charged for incoming calls apparently. I thought I didn't, but then I ran out of balance half way through a phone interview.

https://voice.google.com and a PC headset will get you free calls over the internet.