Just ring CBA up and say you'd like to discuss the rate you are on. I did that once, and they said "are you threatening to move banks?" To be honest, that was not at all my intention - I was just confused as to why a mortgage product with the same name as the mortgage product I had was being advertised at a lesser rate than I was paying. Of course it would have been because I signed up at a different time. But anyway, I said "oh, um, maybe" and they said "sure absolutely we can knock x% off your rate. There you go, it's done."
I presume they just needed a "reason" to put against what they had done. There must be a dropdown field on their screen. "Customer threatening to leave".... "Customer was inconvenienced by a bank error" ..... etc.
Ultimately I doubt that the call-centre operator cares whether you are getting a good deal or not... they just want to get through the day without enduring too many conversations with angry customers. If you ring up and are polite you might be surprised at the outcome.