markcw, RS is clear as mud.
Hungarian numbers are often shown locally as starting 06 12 345 6789 So one might think when told to drop the zero and add the country code when using a US phone that the number would begin as +36 6 12 345 6789. Nope. You dont drop the 0, you drop the 06 and replace it with +36 making the number +36 12 345 6789. Clear as mud.
Here in Hungary with a phone having a Hungarian phone number you can dial either 06 or +36, both will work.
As for wifi calls, yes as the name implies .... I'm on holiday i dont talk on the phone. But if I must talk on the phone I go to a cafe and say "Americano and password please". If I get a call on holiday while out and about I answer if i think its important and pay the cost. Might be 75 cents; longer than that and I call back once I have my Americano.
I have a US phone here in Budapest in addition to my local one. I call it my house phone as its on airplane mode and connected to my wifi. For an American a US phone over here provides some conveniences difficult with a European phone.