Brake Disc Caliper problems of the 2014 Mazda MAZDA6

Rear brake calipers are seized up and the emergency brake no longer engages.

I had my car parked on a hill, it is a manual and I left it running & had the gear in a neutral position with the emergency break on. I was feeding my neighbors pigs when I noticed my car starting to roll backwards so I jumped in the drivers side of the car while it was rolling backwards to stop the car with my foot break. The emergency brake completely failed thank god I told my seven year old son to get of the car while I was helping with the animals! now Mazda is telling me I am out of warranty & I will have to pay to replace both of my rear calipers as they are stuck & replace the rear rotors & brake pads!!! not acceptable! ive taken my car to power Mazda in salem for all oil changes and maintenance and this is the first time they have ever told me that there is a problem with my braking system!!.