First, read through this
Merchant Account FAQ I wrote. It has some good information explaining the basics of Merchant Accounts. Next, to answer your questions. You don't normally sign up directly with your bank, but sign up with a specialized Merchant. The Merchant then processes the orders -- through a Gateway -- that you file through them and then sends you the money about three to four days later.
I don't know much about Merchant Accounts in Canada, but there has to be some. You won't be able to escape the high costs, though, until you're doing a large number of transactions per month. The reason that the costs are so high is because it's so risky for a Merchant to do the processing.