Welcome to the community!
If your contract just ended, your plan was likely a subsidised plan. Until recently, many mobile providers use a subsidised model for their contract devices. This model is different from a tab model or the more recently available leasing model.
With the subsidised model, the subsidy is incorporated into the plan (ie small, large, etc). On the other hand, with the tab model, the monthly plans and tabs are separate. Since the subsidy is incorporated into the plan, your plan does not automatically switch to a BYOP plan at the end of a contract. It remains your previous plan, should you wish to subsidise another device.
That said, Fido recently switched to a financed tab model for their plans. With this model, the cost of plans and cost of devices are separte. Since the old subsidy model didn't separate those costs, you would need to switch to an in-market plan which does not contain subsidy.
You should note that the details of the in-market plans may or may not be the same as your current plan. It is not possible to keep your current plan and merely remove the subsidy.
Hope this helps 😀