Your customers are right. I have a pile of bags in the car because of this nonsense.
This issue is not about just bags though is it. If it were the material for the bags would have been changed and the practice of not charging for them continued. This is about plastic pollution generally. Either it's a genuine issue and research needs to be done to prevent that core problem, or it's not. Grabbing money from the public because one can, as usual, doesn't help.