Im with @rabtech on this one but will only add my experience as it comes to the aftermarket accessories world (Jeep side). Also soon I want be able to chime in on these types of discussions for good reasons.Contact the vendor first and try to work it out there. If not to your satisfaction than further action is reasonable. Just make sure you state all the facts from both sides accurately.
I would even suggest letting them know your plans and email them a draft of your response before hitting the send key. Sometimes this can help both sides see each other's position and a solution found before further actions are required. Hope to never be in such a position but you never know what can transpire or what the causes of the issue are from 10,000 feet.
I really like the idea of sending a draft to the person before publicly posting. I never thought of that. Good one! I just may use it. Or....may not use it depending on circumstances.