Extended Service Plan Cancellation

I AM THINKING OF CANCELLING MY G/S EXTENDED SERVICE PLAN. HERE'S WHY: WE BOUGHT A NEW TO US 2003 NEWMAR KOUNTRY STAR. ONLY HAD 33,500 MILES ON IT, ONE OWNER. I BOUGHT THE EXTENDED SERVICE PLAN FOR THE 4200 MILE TRIP FROM VIRGINIA TO VANCOUVER,B.C. THE COACH HAD BEEN GONE OVER AND FLUIDS CHANGED AND SEVERAL REPAIRS DONE BEFORE THE TRIP.MOTORHOME RAN BEAUTIFULLY THE WHOLE TRIP NO OIL USAGE OR LEAKS ETC. WHEN WE GOT HOME I NOTICED A NEW OIL LEAK FROM THE CAT. MOTOR. THE MECHANIC TOLD ME THAT IT WAS THE OIL COOLER LEAKING. SEVERAL OTHER REPAIRS WERE MADE EG. THE EXHAUST REPAIRED AND A PYROMETER AND BOOST GUAGE INSTALLED. THE CLAIMS DEPT. OF G/S EXTENDED SERVICE PLAN WAS CONTACTED BEFORE THE WORK WAS STARTED, BY THE SHOP'S ACCOUNTANT, AND THEY TOLD THE SHOP I HAD TO PAY MY $500.00 DEDUCTIBLE TO THE SHOP FIRST. THE ESTIMATE ON THE JOB WAS $1349.00 CAN. PLUS MY DEDUCIBLE. THE ACTUAL BILL WAS $1550.00 SINCE THEY FORGOT TO CHARGE FOR THE CONTAMINATED ANTIFREEZE AND 1 HR. LABOUR TO PRESSURE TEST THE COOLING SYSTEM FOR THE OIL COOLER. WHEN I PHONED TO CHECK ON MY CLAIM, THE Y SAID THE CHEQUE WAS SENT. SURPRISE! BUT ANOTHER SURPRISE: ANOTHER $500.00 US $ FROM THE CHEQUE. BOTTOM LINE PAYOUT IS $510 US. G/S WOULDN'T COVER THE ANTIFREEZE OR PRESSURE TESTING. VERY REPUTABLE SHOP AND FIRST RATE WORK. WHY THE NO COVERAGE ON THE WORK? AND WHY THE DOUBLE DEDUCTIBLE? MY $2000.00+ JOB WAS ONLY COVERED TO $625.00 CAN. CAN YOU EXPLAIN...THANKS.