When pronunciation trainers say that a student is pronouncing something “wrong”, ask yourself what is “right”. If you can’t be understood, then that is wrong. But, if you say butter with strong TTs (not Canadian DDs) then you’re speaking the queen’s English and are corrected in some language classeswest coast Canadian classes.
Hold on to your unique accent, as long as you can be perfectly understood.
However, tell your teacher that you do want to speak like a true west coast Canadian (as there are hundreds of Canadian accents). We will turn your “I have to call them” into “I’ve gotta call ’em, eh”.