Welcome to the community!
Firstly, as per the Wireless Code, all devices purchased in Canada after December 1, 2017 are sold unlocked. If you purchased a device which was manufactured prior to that date, the device might have been locked by the manufacturer, however, you would be provided the unlock code with no charge.
What do you mean by downgrade your plans? When did you purchase the phones? Have your contracts finished?
If your contracts have completed, your contracts would have been with subsidised plans. Subsidised plans incorporated the cost of devices with the cost of plans. You would need to switch to an in-market plan in order to have a plan without subsidy. It is not possible to simply remove the subsidy from your current plan.
You should note that Fido recently switched to their Payment Program, separating the cost of devices from plan costs.
On the other hand, if your contracts have not yet completed, there would be a downgrade fee to switch plans between categories (ie from Large to Medium or Small). The downgrade fee would be the difference in subsidies between the categories. That said, you can switch to different plans within the same category without downgrade fee as the amount of subsidy would be the same.
Hope this helps 😀