no unlocked SIM-card = no access to any operators network = no data/voice traffic possible = no costs. you can't call anyone and they can't call you. same for data (unless, you have WLAN connection..)
as I said, the drawback is that you can not receive/make calls or SMS/mms.
EDIT: @ED. Just choose "ok" instead of "enter pin code". You wont be able to do anything which means that traffic goes through an operator network until you enter your pin-code.
#5049335, By Lave Going abroad with an iPhone
Lave 302 posts
Seen 20 hours ago
Registered 9 years ago