Hello Frankm5b,
Welcome to the community!
I understand it might be alerting to find out the number you received may have already been registered for other services, such as WeChat. However, that can be a normal situation. In fact, it can happen with other similar messaging services as well (see here).
As mentioned in that post, the number of phone numbers is finite. From time to time, new overlays are created to expand the existing number allocation. However, with the number of users ever increasing, even those overlays fill are quickly exhausted. 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 while the number you received from Fido may have been previously been owned by someone else, it wouldn't have belonged to anyone else when it was given to you.
With regards to the number being previously registered to WeChat, the previous owner of the phone number did not deregister that number from that service. If you are unable to register that number with WeChat, you might consider contacting their customer support and inform them that you are the new owner of that number.
Alternatively, you might consider changing your phone number. However, there would be no guarantee a new number hadn't also been previously registered on similar messaging services. You should be able to change your number via your My Account --> My Usage. From your Dashboard, the option to Change Number is near the bottom of the page under Quick Actions.
Hope this helps 😀
Cheers
