Vitality Drive Cash Back rewards forfeited

Discovery's massive 25% hike from October on monthly premium totally unacceptable. My Instruction on 4th October to cancel insurance form 31st October. Confirmation received effective cancellation date 31st October. On 11th October was informed my September cash back earned was R585. On receipt of this the sum earned would appear in my bank account. This was not done, reason given forfeited on grounds of cancellation. Cancellation date was 31st Oct not 4th October , I can understand cash back rewards earned in October would be forfeited. My wish to escalate complaint to higher level ignored. Moral of story Discovery prefers to keep clients money in their pockets through devious manipulation of rules.