Normally if you heard that message, the number wasn't entered correctly. Did you enter the number in the format +1.xxx.xxx.xxxx? Also, did your phone work in the past?

I did and same result

It worked perfectly until today

Can you reset network settings of the phone to see if it can help? 

I assumed you have checked your self-serve to see if everything was ok? Also, can you dial 611 or your own voicemail?

How do I do that?

I cannot 

Which phone are you using? Normally a reset network settings should be in the settings.

Also, have you tried to restart your phone, take the SIM out and put it back again?

I have done all of this to no avail

This is weird, are you a prepaid or postpaid customer?  Do you have Koodo signal in your area?

I'm a prepaid customer. I think I get Koodo signal as I can send and receive text messages.

Can you check your prepaid selfserve to see if you still have minutes in your plan? Did data also work?

also, which phone are you using?

I still have minutes and I'm using a Samsung Galaxy A71

If you had another phone to try, I recommend you put the sim in it to see if the issue follows. You can also visit a Koodo kiosk to ask a rep there.

It was a technical issue on Koodo's part. The issue is now resolved. Thank you very much for your help.