Welcome to the community!
Sorry to hear you're thinking of leaving Fido. If you would like to keep your phone number, you would need to inform your new provider so they may request the port-over from Fido. Once your new provider requests to port your number to their services, you should receive a text message to which you must respond in order for the porting to proceed. It is important that you do not cancel your Fido services prior to the port-out being completed. Once the port-over is successful, your Fido line will automatically be cancelled. You can find additional information here, here, and here.
With regards to plans from other providers, make sure you're comparing similar services. While some plan offerings might seem cheaper, they might cost less because they also include less services.
Hope this helps 😀