In Ontario you are stuck with either Rogers/cable or Bell/ADSL or one of the resellers acanac/teksavvy that use bell or Rogers networks.
The problem with bell is that there internet service goes through telephone lines which is bad if youre in an old area especially if the telephone lines are ran above ground to home/workplace. Also helps to be near a telephone switching station to get decent speeds too. So depending where your office is, your probably SOL.
There's more than just Rogers in Ontario. In fact, one of his branch offices is located in a territory served by Eastlink, not Rogers. There's also huge swaths of Cogeco in Southern Ontario, and little bits of Shaw - particularly around Hamilton - here and there.