Are you a prepaid or postpaid customer? If you are a postpaid customer, you can suspend your service in self-serve https://www.koodomobile.com/en/help/reporting-your-lost-or-stolen-phone

And No, there isn’t a way to receive call if there is no SIM in your phone.

Yes, I am using postpaid. Now, the situation is that I am in my home country, not in Canada at the moment. I left my SIM at home (Canada), and now when my friends call me on my number, my number rings. I am worried now because I cannot connect to customer service and don't know how to fix this. Please suggest something. 

Have you looked into the link I sent above?. You can suspend your sim card in selfserve.

Yes, I did check. Since I have already left the country, it is

Asking me to connect with the Facebook team; however, the link is broken. 
Now What shall I do?

Could you please provide a direct contact number for customer care? I need assistance in suspending my services, but when I attempt to reach customer support, the automated response indicates that a text or callback will be sent to my number, which I currently cannot access.

Is there an alternative way to proceed with this request? 

There is no direct number for customer service. As I mentioned above the digital assist should be able to suspend your service. What specific error did you see? Facebook can also be used if you are overseas. Links are below at the bottom of this forum page

Anyway, if the SIM card is at home in Canada, it should be safe.