Without knowing what phone you have, it is impossible to give you an answer. But, if your phone is compatible, at the very least it will need to be unlocked. It might well be worth scrapping it and buying a Speakout phone + a $50 voucher. You'll get $20 off the cost of the phone.

As to your Bell issue, my guess is that you are getting texts from a subscription service like "joke of the day" or something similar. These things can run at about $5 a text and will drain your account before you realize what is happening. I had the same issue with Virgin.

Seeing as you got the phone at Costco, I'd just return it for a refund. They're pretty liberal that way.