M Phone

SIM Free mobile phones are those that have been unlocked so that you can use them for any network that you desire. If you previously had service with Orange and had the phone unlocked you could use it with O2, however some or all of the features you were able to use with Orange may not work with O2. It depends on the brand of the phone and the type of features you are planning to use.

SIM Free is good because it gives you felxibility in which carrier to use. This way if O2 offers a better plan then Orange you can easily switch without having to worry about getting a new mobile phone and vice versa.