Why is Telus selling services to international criminals?

You will need to see if your provider offers a similar service to Telus' Call Control. If they don't then you'll have to make a choice. The scammers are calling from overseas using spoofed numbers. And yes the scammers do spoof caller ID so that they display numbers that actually exist but have no connection to them. Call blocking on your phone is useless if they simply change numbers and get through again. 

A lot of scammers use VoIP services like TextNow that will give them a Canadian phone number and the ability to receive calls on it as well. Phone numbers are portable / transferrable these days so a number that was associated with one carrier can easily be changed to another. Telus very well may not even own the phone number any longer, if they ever did. YellowPages isn't an accurate resource in determining the ownership of a phone number.  datacorelookup is also not accurate in the majority of phone numbers I tried looking up. They had the provider wrong in so many cases and in almost all cases they had the usage type wrong as well. I know a number of people using Shaw, Rogers or Bell for phone service and the websites all list those numbers as Telus. Neither website even indicates where they are getting the provider information from or how recently they got it.