Hello Zehlek1,
You are correct in that the system won't allow you to do the change online because you have a Québec plan. You would be able to keep your old Québec plan and phone numer, though you should note that people from Ontario calling your phone number might incur long-distance charges. You would also need to verify your plan included Canada-wide minutes.
Whether or not a change would affect your contract would depend on your plan type. If your plan is subsidised, you would need to get a plan within the same subsidy level. However, now that Fido has recently switched from their old subsidy model to a financed Payment Program, I'm not sure whether any of those options would be available anymore. If you did need to switch from subsidised plan to a new plan, you might be required to pay the balance of your device.
If you would still like to change your phone number, you would need to contact customer service. In addition, they can also be contacted via Live Chat, Facebook, or Twitter. Those methods can be accessed via the contact page posted above. There would not be any fee for the change since your move involves a change in local calling area (see here).
Hope this helps 😀
Cheers
