Why have I been charged £5 for visiting Greece

[Gloria3]

What have I been charged £5 for visiting Greece 

[Gloria3]

That should be why 

[madasaf1sh · Accepted solution]

@Gloria3 

For you to have been charged, your phone will have connected to one of the countries bordering Greece such as Albania or Turkey, which are not part of the EU so chargable. 

It will show on your bill the country you have roamed in. 

This also has nothing to do with o2 when it happens, as it is your responsibilty to ensure your phone connects to a network int he country your are visiting.

Accidental roaming occurs when you're in an area close to a national border and your phone picks up the network across the border. If this happens, you may be charged as though you were roaming in the country across the border. You can prevent this by choosing manual, rather than automatic, network selection on your handset and then manually choosing the O2 network. This way if you lose the O2 network, your handset won't try to connect you to a different one. For help with turning off data roaming, go to our interactive device guide.

This is meant for NI customers but applies in your case