I have had Koodo for years. No problems even living 2 hours north of where I am now. I moved to Caledon, Ontario where they supposedly have great coverage and my Samsung Galaxy SIII gets no service. I sometimes get one bar but mostly it just says"emergency calls only".
Emergency Calls Only means you have service, but your SIM is not working properly. I suggest the following:
Restart your phone
Turn off your phone, remove, then reinsert your SIM, and restart your phone.
If the above fails, see what happens if you insert your SIM in another phone, or another SIM in yours.
Finally, see if another SIM from a Koodo shop works in your phone.