John O'Neil Johnson Toyota broke my car audio unit and wont compensate me Meridian, Mississippi

I bought a car from John O'Neil Johnson Toyota. Part of the deal was that we would switch out the stereo systems in my trade-in car. I was an out-of-town buyer. The agreement was that I would ship the original 'stock' stereo unit back to them, and they would remove my new upgraded stereo/audio/GPS system from my trade-in and ship it back to me.

I fulfilled my part of the bargain, but the dealership jammed my expensive stereo unit into a small box without packing material when they shipped it to me. It arrived damaged. The dealership refused to pay for the damages. 

My observation is that this dealer talks a good game before you buy the vehicle, making it sound like they really care about you and want you to be happy with your purchase, but after you drive the new vehicle off the lot, YOU'RE ON YOUR OWN.

It even took them many weeks to send me the extra set of keys for the car, despite my many messages and phone calls and emails. 

Also, they also told me that my vehicle would get up to 23 MPG, and the best I've ever gotten is 17 MPG. Like I said, after you drive the vehicle off the lot, YOU'RE ON YOUR OWN.