Meineke Car Care Center review: Incorrect muffler recommended and installed

I called Meineke and asked for a Factory replacement muffler for my Dodge 2500 Ram. They said we have one in stock just drop it off.
Four hours later they call, "sorry we do have that one but we have one just like it in size and its $20 cheaper". I asked it will fit the same? They answered yes.
I agreed to buy the recommended part.

I do not drive this truck much so it was a few months later when I did drive it and the tail pipe fell down. I reattached and a little later it fell again.

I have worked over 30 years as a programmer for the army so I don't know much about mufflers. I took them at their word that the part would fit.

My son was in town and took a look at the muffler and said "they put a popper on there". My response was, "What's a popper". We measured the muffler that Meineke recommended and installed. It's 3 inches longer than the factory muffler and that's why my hangers don't line up and it keeps falling off.
My son went with me to talk with a manager at Meineke. The manager on duty at that time was a different manager than the one who recommended the replacement muffler. We told the new manager about what had happened. His first response was, "We do not install Poppers. You must have gone somewhere else". I said no it was at this location (Ballwin, MO). He then checked the records and sure enough it was there in black and white, 'Installed Popper on Ram truck'. I asked him to compensate me or provide a discount on a new muffler. He didn't even hesitate to say, "No, I have to pay shop time, his welding time, etc. Sorry".

We left in complete disbelief of what just happened. Their own records show that they installed a faulty muffler and all I asked for was them to work with me. The accountability and customer service of this facility is very poor.