Mid/rear Seats Assembly problems of the 2008 Mercedes Benz E350

I smelled strong gas smell a few days ago. I took my car to mercedes arrowhead located in arizona yesterday. They informed me that the problem would be covered under a 15 year warranty (fuel tank had started leaking). Today they called me and said that the leak had saturated to my back seats and that it wasn't covered because I had taken too long to call them and that's why the back seats were saturated with gas (I didn't know that my seats were saturated with gas until I started to smell it through my vents while ac was blowing). Now, I am being asked to pay almost $500 to replace the pads and deafening material as they told me it wasn't covered by warranty even though it was caused by a defective fuel tank. At this point I'm not sure if there have been any health related issues for myself and my 2 kids who normally sit in the back of the car who has been inhaling the gas fumes for an unknown length of time.