With pay as you go or other account setup if the billing is overdue then calls cannot be made in or out. At least people should be able to call the number to ensure contact in emergencies. Some countries operate that way and it is very helpful. This was a problem when my son was pay as you go and would forget to top up.
You can top up through the My Telus web interface. You can set up automatic top ups. You can buy a voucher at a retail location and call 611.
Canada charges for calls in both directions. Allowing incoming calls without an account would be problematic, as there is no way to determine when the account becomes inactive.
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Those countries that "operate that way" charge the calling party for the airtime. So people can have prepaid phones and not pay airtime for when they are called.
That's why you see different long distance charges to many countries when it is a landline versus a mobile.
I'd certainly much rather have it the way it is here than to pay someone else's airtime when I call their mobile. I believe that the phone should still be able to call 911 for that type of emergency.