BAD EXPERIENCE!!!!

A took out a policy with SA Warranty last year and all the components covered were sent to me. All my premiums are up to date and everything is fine with my policy. I called to enquire a day before taking my car in for service whether brake discs will be covered on my policy. I then took the car in and was advise they will only insure/payout half of the amount even though after investigation it was deemed not wear and tear, HOW IS THIS POSSIBLE???!!!. THIS AGAINST EVERYTHING THAT THEY HAD TOLD ME AND IS UNACCEPTABLE.