new holland 6730

I bought a 2015 brand new New Holland 6730 in 2016 I mowed twenty-five ac last year with no problem. This year I mowed about ten ac. and the gear box froze. I took it back to the dealer here in Ky and they found that the gear box was frozen due to no oil in it. They rebuilt it and I was told it was under warranty. I went to mow again and I got about an ac mowed before I had another problem. I took it in again and this time I was told there was a broken shaft which is suppose to break under stress. Two of my blades were bent and they were hitting the bar which they said caused the bar shaft to shear. I was then called into the office and was told that the unit was not under warranty when the first problem happened. I was also told that i had bought the unit in 2015 which was wrong I thought, but being 73 I thought I could be wrong but I was not. So now I am being told I have to pay three grand for the first fix and that it was my fault that the blades bent and were hitting the bar. I am willing to pay for the bar shaft fix. But why has New Holland denied  the first claim. i was also told by the owner of the dealership that when cutting grass that the mower should be several inches above the grass. Now this unit has skid plates which I thought were meant to ride along the ground. I am new at this and I could be doing things wrong but a leaking gear box is not my fault. Can anyone give me any insight as too what I am doing wrong.

thanks

rick

new holland 6730