The mobile networks in Canada are quite competitive and expensive these days, and you'll need to do some shopping around to find something that would suit you. Are you planning on getting a new mobile as well? This would affect the cost of a plan, should you want to sign a contract.
Have a look at this review of some of the top mobile networks in Canada. If you plan on using the Internet on your mobile quite often, you'll need to factor in the amount and price of data in your plan. Rogers, Bell and Telus are all popular choices.
When are you planning to move to Toronto?