Sim cut will work unless you have incompatible SIM :) A SIM that has really big contacts which look more like a globe than square. That's what I had from O2 in Ireland and it didn't work in One X.
So I went to O2 store, asked for replacement and got it after 1 minute of waiting, free of charge, already activated. They did not ask for old SIM, they simply deactivated it. Can't be any easier really
Previous: Asus Padfone 2, HTC One X, Samsung Galaxy Nexus, Samsung Galaxy S II, HTC Desire Z, HTC Touch Pro2, i-Mate Ultimate 9502, iPhone 3G