Trying to book - Hopeless service

I tried to book on the website for Sabi Sun for 2 nights, selected type of room and rate . when it came to payment, system refuses to allow Sunrands but requires card payment. When I phoned the Call Centre to complain that my sunrands were being refused and Credit Card payment was required I was given various excuses from it is a special, to the room is different until they connected me direct to the hotel. The hotel also had various excuses. Bottom line - why dont they want me to use Sunrands? Or is the Sunrands rewards programme just a ****