Hi, I'm Ashik. Welcome to JustAnswer. I'm reviewing your question now, and will post back with your reply ASAP
You have two options in here. If your cell phone is unlocked to use around the world, then you can take out the SIM from your phone and put in a local SIM card from Canada. This will allow you use that SIM card. Your number will be changed. This is the best solution if you are staying in Canada. If your cell phone is not unlocked, then you need to call your service provider (AT&T, Verizon) and request them to unlock the phone for you.
Another option is, you can contact your service provider (AT&T, Verizon) etc and you have to ask them to activate or enable the International Roaming Package on your phone. Then only you will be able to use that SIM card from USA on Canada. This is suitable if you are staying in Canada only for a few days and want to keep same number. In Roaming, the call and data charges will be very high.
In both ways, you have to contact your service provider/carrier network of USA. If you tell me who your service provider/carrier network of USA was, then I will find their contact number and send to you.
If you have any questions or would like any additional information, please let me know.
Just checking. How is it going ?