Orange normally lock their phones so you will have to unlock it,,, you can try and phone customer services telling them you are going abroad on holiday and want to unlock your phone,,, T-Mobile done this for me for free I happened to say I was going to be using T-Mobile USA.
If Orange make you pay to unlock the phone below is a useful website you may find useful, or google it and you will get plenty of options some more user friendly than others.
Kind regards,
Brian,
http://www.unlockthatmobile.co.uk/in...FQ_llAodkWFoQQ