Unfair Practice - Dissatisfied customer

My brother is the principle driver of a vehicle costing R500 000 incl. finance charges he sourced quotes for motor insurance and momentum came in at the lowest. He disclosed all the information to his broker and was accepted and covered with Momentum effective 07 July 15. The car was only released from the dealer after the insurance with Momentum was accepted. Now a month & a half later Momentum cancels the agreement with 30 days notice ending 17 Sept 15 stating the risk is to high, my brother is 35 years old, he is not an irresponsible driver. Momentum according to the broker Ben Badenhorst is being very lenient and will honour any claims till 17 Sept 15, how kind! I am totally disappointed in the manner that Momentum handled this matter without discussing the matter with my brother & taking into consideration that Auto and General covered him after ABSA Idirect. Momentum created a false impression by accepting him & based on that the purchase of the car had been finalised. The car will not be covered from 18 Sept 15. Momentum has acted in bad faith and placed my brother in a serious predicament. Momentum to revisit this case & reverse their decision or legal advice will be sought