How to know if my iphone has been unlocked?

I asked Vodafone to unlock my iPhone 4s and they said it would take up to 7 working days.
when will I know It has been done, will I have to phone them or can I just check when I want?

They might send u a message if not you can check by putting another sim in such as an 02 and if it says 02 or whatever provider in the top right of the screen it's unlock if it isn't unlocked it will say no service

Have a SIM from another carrier ready after that time has passed to see. If not, call them about that.