I don't know of a Canadin provider that does day-by-day pay as you go, unless you just grab a phone at 7-11. Unless you are out of the city for a portion of your trip, it might be best to grab a Wind sim card and do a prepaid month.
$30 for unlimited everything.
edit: To compare to the 7-11 phones, 100 mins + unlimited text 100mb data is $30. It doesn't look like you can add the plans for just a few days though, has to be 30 days. The non-value plans cost about 25 cents/min, so that is way more expensive.
http://www.speakout7eleven.ca/prepai...one-rates#data