You need cash credit on your account to pay for international calls - 50c/min. There are probably cheaper alternatives to be honest.
When calling Albania, Andorra, Armenia, Austria, Azerbaijani Republic, Belarus, Belgium, Bosnia and Herzegovina, Bulgaria, Channel Islands, Isle of Man, Croatia, Cyprus, Czech Rep, Denmark, Estonia, Faroe Islands, Finland, France, French Antilles, French Guiana, Georgia, Germany, Gibraltar, Greece, Hungary, Iceland, Italy, Latvia, Lichtenstein, Lithuania, Luxembourg, Macedonia, Malta, Martinique, Mayotte/ Reunion, Moldova, Monaco, Montenegro, Netherlands, Norway, Poland, Portugal, Romania, Russia, Serbia, Slovak Rep, Slovenia Rep, Spain, Sweden, Switzerland, Turkey, UK (incl NI) or Ukraine you'll pay:
|Calls to mobiles and Landlines||50c|
All International call charges are inc VAT and are charged per minute.
Note that calling NI using the 048 prefix rather than 00 44 is normally more cost effective:
Hope this helps.