What should I do about this bill?

I have a mechanic that i have used before and have in-store credit with. they replaces an axle on my 4x4 truck that goes to the tire. it turned out to be the wrong axle and fell off on the interstate and cost me a day of work. he took both of the front axles off temporarily turning it in to a 2 wheel drive so he could order the right part. now i get a bill for the wrong part because he says its not refundable and the labor to put it on. also the labor to remove the other axle so he could order the right part was included. am i the only one who finds this a little shady?

That is absolute bull, you should threaten to take him to court over the charges. It's his job to get the right part for your vehicle when he goes to repair it, and he put the wrong one on. Not to mention, he endangered your life. I can't believe it fell off on the interstate, you're lucky you're not dead! Tell him you're not paying, if he fights you on it, threaten to take him to court, if he says fine, then go find a lawyer, you will win this case if it gets that far.

This was the mechanic mistake. Plain and simple, it's his responsibility not yours... Oni is right, if you do go to court have your lawyer make him pay your layer bill also and time off work.