Three has become the first UK mobile network operator to abolish international roaming charges in the countries where it operates.
Three has launched a new offer called 'Feel at Home', which allows Three customers travelling to:
Republic of Ireland,
Australia,
Italy,
Austria,
Hong Kong,
Sweden
Denmark
USA (Dec 2013) addendum.
Addendum ( 5th June 2014)
New countries added from 1st July.
France
Switzerland
Israel
Finland
Norway
to use their UK price plan to text, call and use data without incurring international roaming charges.
HERE