So here is the question, should I buy a Nokia C3 from 7-11 and take advantage of the 1/2 price phone ($60) plus the $40 bonus or buy it from Futureshop for $70?

The reason I am asking this is, I want to unlock the phone and use both the SO in Canada and a US carrier in the USA as I travel across the border regularly. I understand that the SO C3 may not be able to be unlocked from services like cellunlocker. But I also understand that there is no difference in the phone and either sim card will work (rogers or SO). Is there anyone who has unlocked a C3 from SO? It would be cheaper to buy from 7-11 but if I can't unlock the phone it's a paper weight 50% of the time.