American using cell phone in Europe for the first time.

My son is going to England, the Netherlands and Portugal this summer for three weeks. I have never left the US and am at loss as to how to explain using a cell phone while abroad to him.

We have a GSM phone that was purchased in France last year that accepts SIM cards. I am told that he can purchase SIM cards in most public spaces in Europe. I am unclear as to how that creates a phone number for the phone, and how you add more minutes onto the phone. Should he use a prepaid calling card to call the US? Will he need a different SIM for each country, or is there one that will work throughout Europe?

When a friend’s daughter went to China, she had a cell phone with a SIM that was linked to a credit card. Unfortunately, when she went from China to Hong Kong, she had to get a different SIM, and lost the original one that was tied to the credit card. Not realizing it was lost, she didn’t tell her parents. Someone found the SIM and ran up over $800 in phone charges, with the company refused to write off because the SIM was not reported lost.