Yep, just go into an O2 store, pick up an O2 micro sim (it's free), then go to
www.o2.co.uk/swapmysim and follow the instructions.
It usually takes about an hour for the network to make the changes. You'll see your phone service cease on your old sim. Then put the new sim card in and turn the phone back on, and it'll activate and job done.
