Hi Steve, yes it just goes on your phone bill, I've not had any surprises with it, just make sure you always make the calls from a landline.
That is a problem for me as I don't own a landline, just use my mobile. Been trying to reduce costs to save for spouse visa so cancelled it. Maybe its costing me more.
,
o2 your country list,
o2 my country minutes,
02 your country,
O2 your country minutes,
o2 your country free minutes,
o2 your country number,
how to switch o2 your country