You have to get a data plan, but you have an option.. unfortunately, it will cost you some money.
Sign the contract with the iPhone, pay $199/$299 respectively for one the devices.
Then call one of them and cancel data. Rogers/Fido it costs $100 to cancel it, not sure about Bell/Telus (although it's probably the same thing).
This is your only option unfortunately because the reps at the stores have no control over this, no matter how much you kick and scream. So if you want no data, just suck it up and pay the $100 now instead of paying an extra $30/month for data that you won't be using for the next 3 years.
Reps on the phone, on the other hand, do have control over your account (about 99% control I'd say, as they can do absolutely anything), however... being a new customer (I'm assuming since you've asked about the big 3) they won't do much to help.
Oh, and be sure to block all data on your phone!