We live right on the U.S.A./Canada border, why am I always getting warnings about roaming charges and why do I have to keep a very careful watch on my bills. Yes, I know I could move, but I could also move to another company?
You will probably experience the same problem with another supplier, but it's an easy problem to fix.
Go into your phone settings for preferred network and choose Koodo manually. When that setting is on automatic, your phone will latch on to the strongest tower, which may be an American one.
As a tiny bonus, you may well have service a few kilometers into the US without any roaming charges because your phone will hang on to the Koodo signal till it peters out and ignore the US towers entirely.
Change the settings back to automatic whenever you really do intend to use US roaming service,