Not sure where to buy 'em (prolly get 'em online) but there are some International call cards for mobile phones. They look somewhat cheaper than hotel rates.

Newsagents sell them. So to supermarkets. you call an 0800 number (or equivalent), key in your card number, then the phone number you want and hey presto. You can get calls for a few pence a minute. The higher value of card you get, the better rate you get, usually.

That said, all this is from when we sourced them out for MIL a few years back, but she still seems to be doing it this way.

Well, what happened was that the people she's travelling with rented a phone from Verizon. (We investigated a rental, but at $30/week it didn't seem worthwhile for what we needed it for.) Cost: Outgoing calls to the US, $1.60. Incoming calls, free. So she borrows their phone, calls us, hangs up before we answer, we see the caller ID, and call her back on the Philadelphia-area mobile number (which forwards to the one in the UK).

Oh, so you're not cheap, you're a control freak.