In a free market it is important that when you are displeased with a supplier that you truthfully tell that supplier why you are displeased (ideally very vocally) and are actively considering alternatives. It is one of the few early-warning signals that might change their behaviour.

But ideally, just stop giving them money immediately and tell them, but mention that you are willing to change your mind if they change their behaviour. And if they vascillate too often between what is right and what is profitable, inform the entire system even if it is a great personal expense. As long as it benefits the system, you will come out okay in the end.