Does Nunavut have Telus/Bell hspa coverage, Sandra? Do you already have Koodo service? In that case you can just purchase a nano SIM card and activate it in self service. Otherwise, you'll need to sign up for a plan... unless you want to go with prepaid. Can you tell us a bit more?
Looks like telus does offer coverage in some regions of nunvut with the 3g and LTE networks:
This should mean most reasonably new smartphones will work up there, at least any of the phones koodo has on offer, as well as any iPhone sold in Canada.