Hi,
I am currently using mobilicity cell phone plan which gives me unlimited US and Canada calling with many other features.I am paying 22.50$/month now but as I got this plan with an offer so it s a reduced rate .Original rate is may be 45$/month but if you opt for multi month payment plan(pre payment plan)it might be reduced to 36$ or so.The voice quality is also quite good.
You can see their plans at mobilicity.ca