Look for plans aimed at business users. The providers tend to load-up consumer plans with features aimed at heavy multi-media using youths.
If your usage is high (minutes and LD) but the number of distinct contacts small (i.e. most calls are to office, home, same telephone numbers) you might win with a favourite-five, favourite-ten option that includes North American LD. These will give you unlimited calling between your chosen numbers and may be less expensive than making North America your local calling area. However, watch for roaming charges when you are in the USA; you may be able to call US numbers from Canada but not call home when you are in the USA. Again, some business plans offer discounts on roaming.
Sadly, not all clients are equal. Users who work for big, national corporations have access to plans and rates, for their personal use, that shame the published consumer rates. The rest of us are out of luck. i spent my career in the public service where such a "deal" would be considered a potential conflict of interest and where it was expressly forbidden to ask for or accept the "government rate" when checking into a hotel or renting a car for personal use. As a "regular consumer" I pay more so others can enjoy their corporate perks.