The national company is Bell Canada (http://www.bell.ca).
In Montreal there is only one company, Bell Canada
(http://www.bell.ca) that can install or repair
a line and provides local calls. All local calls
are free and different phone packages are available
for long distance and overseas.
By default it is also your long distance phone
company but you can call any other company up
and register with them for no charge. You now
have several choices who are currently in a price
war. It's a good idea to shop carefully and read
between the lines.