When you become a 1pMobile customer, international calling and roaming are enabled by default. If you are visiting zone 1, calls to standard UK and Zone 1 landlines and mobiles will still cost just 1p. Calls to landlines and mobiles outside Zone 1 will cost the same as the UK, receiving calls and messages is free. Texts outside zone one will only cost 9p, and mobile data will be 1p a MB.
Visit the special international and roaming page on the 1pmobile website to see the roaming charge of the area you are visiting.