Monro Muffler & Brakers They do not want to honor lifetime waranty for my muffler Allentown, Pennsylvania

I installed new muffler in October 2011(1 year and 2 months ago) to be exact, and went this week to repair a flat tire and had them check my muffler, and it happend to have a crack on the seam where they welded it. and they claim is out of warranty after 1 year. They have false advertisement, because when they repaired it I gave them a coupon they sent me for lifetime warranty, and they promote it as lifetime warranty on the internet. They claim that if they do not have it in stock, the warranty is from the manufacturer. But I did not fixed this d**n thing at the manufacturer, but their business..