Discovery Refuse to Pay out saved Fuel Rewards

I was insured by Discovery Insure for many years until Nov 19 after which I was offered a much better deal by Santam. The problem now arise that Discovery DO NOT want to pay out my 'saved fuel rewards' which is normally paid out on a monthly basis. I decided a few years ago to NOT take the monthly 'fuel' rewards, but to rather save it with Discovery to cover any future access payments. Discovery now state that if and when you cancel the insurance, the insurer forfeit the rewards. This is however unacceptable as it is rewards that was 'earned' and should be paid out without any hassles !!