I haven't found a Canadian cell provider that can compete with the lower prices and more data that the US providers have. You can probably call forward your Canadian cell calls, and if you have an unlocked cell phone pull out the Canadian SIM card and replace it with a US prepaid Sim card (for example AT&T go phone). This works well for us.
Not sure if you have a home phone or not,I dumped our Bell account for a Vonage VOIP phone service (much cheaper), they have a neat app called extensions for smart phones that lets you call and receive calls from your home number anywhere you have internet connectivity, you don't use your cell minutes.
Depends on your Carrier. I'm with Telus and on there new Canada/US plan. It actually cost me the same amount I was paying before. But I am not in a contract. No roaming fees. Use my phone for calling, texts and data in the US just as I would in Canada. No additional charges. Love it! I pay $85 per month for 6 GB of data, and the Can/US plan.
I would guess you call your Canadian cell carrier. They probably have a $ program. Last time I was in Canada, (for a month) my carrier (Verizon) had a program for, I think $10/month to use my US phone in Canada.