I want to replace my 2nd phone, dont want to spend too much on it hence why i'm looking at these.

http://www.argos.co.uk/static/Produc...e%2Bphones.htm

http://www.argos.co.uk/static/Produc...e%2Bphones.htm

But which of those can be unlocked by free code as i have an O2 sim i want to use (my old number)