TQL refuses to pay for delivered load !

I hauled a load of printed materials from Minnesota to Ohio over two months ago with four drops at post offices. TQL set up the appointment times. The first drop off went without incident and I made my way to the second drop at Cleveland, Ohio and arrived before my appointment time of 18:00 hours. At 22:00 hours one of the supervisors informed me that my drop shipment did not have priority and that thrid shift would get to unload me in the upcoming hours. At 04:00 hours, I was informed that they unloaded me and the supervisor handed me the signed postal acceptance form.
I pulled out from the dock, closed the swing doors and continued to the third drop which was 30 minutes away. When i arrived at the third drop, I handed the bills to the supervisor and I was told to back into an empty door. A few minutes later, the same individual came back out and informed me that there was no freight in my trailer. The employee immediately knew what the problem was. The previous drop at Cleveland took everything off my truck and assumed all the freight on board was theirs. The supervisor then invited me into his office where he then called the Cleveland distribution center and informed them of their screw up. After a few phone calls back and forth, the supervisor told me that Cleveland verified that it was all there and not to worry about it, since they will just foreward the self addressed magazines to them through their own trucks. The supervisor then signed the form in the proper place indicating that he received the shipment. He even took the time to call the fourth and final drop off location to give them a heads up on what had happened. When I arrived at the forth location, I was greeted by the third shift supervisor who knew what had happened. He was very friendly and took 15 minutes to write a short story of what happened and Cleveland had the freight, but he would not sign the form in the proper place which indicates that he actually received the shipment, which he did not. He explained that if he signed it stating that he had taken physical possession of it when he did not have, it would be grounds for termination by the postal service and he was two years short of a 30 year career. I cant say that I blame him for covering his ###, especially when the postal service is trying to downsize and is terminating employees. He signed the form on the back below the short story he wrote explaining the screw up at Cleveland and my compnay forewarded the bills to the broker for payment.
After numerous calls to Total Quality Logistics, they are refusing to pay us for the run based on the fact that the official postal form was not signed by one of the locations in the correct place.
Do yourself a favor and stay away from TQL. They are thieves.