What plan do you have? 
Did you make calls while you are in Canada or you were in USA?  

I have a post plan 10GB and I made 3 calls to US from home in Toronto.

So, you have a $39 plan. It doesn't include International long distance calls.

If you've been charged for easy roam, that has nothing to do with long distance. It means your phone connected to a US tower. If you were in Canada at the time koodo will credit you for the charges, but you'll need to talk to them directly, either by setting up a callback or via Facebook Messenger.

If you manually search for networks on your phone and select Koodo that should prevent it from connecting to American networks, but you'd need to do so again every time your phone is restarted.

how can I reach out Koodo. The option to reach customer service it has been off for few days

Click Koodo assist to set up a call back.

But, you made long-distance calls without perk or add-on. So the charges are legit. A rep might be help you, but it not guaranteed...