We use these all the time when in the US. We buy the
AT&T International Pre-Paid card, usually from Publix, (
Walmart, Walgreen and the fuel station shops also have either these or similar versions) that costs $10 and gives something like 200 minutes calltime to the UK - brilliant value!
A couple of things to watch with these:
- some hotels will still charge a connection fee for the calls made from the phone in your room, even though you dial a free-phone number
- using the card from a call box deducts a set charge from the card before making the call (something like $1.50?)
- if you use an international card to call a US number it uses a lot more of your credit than calling the UK!