Hello Ishan_mazzn,
Welcome to the community!
Yes, the practice of recycling numbers is commonplace and necessary. Generally, there is a minimum period where those cancelled phone numbers are not in circulation (see here). So the number you received from Fido wouldn't belong to anyone else. Unfortunately, there may be situations where websites, apps, or other institutions might not have been updated. In such cases, it might be necessary to contact the website, apps etc support teams to inform them you are the new owner of the number.
That said, I understand you wish to change your phone number. You should be able to do so via your My Account --> My Usage. From your Dashboard, the option to change your phone number is near the bottom of the page, under Quick Actions.
Hope this helps 😀
Cheers
