SAA breaking their own flight change terms and conditions

We recently had to move flights after our visas did not arrive in time. The SAA specifies that a R1700 flight change fee is payable, as well as the difference between the new air ticket and the old air ticket in the event of the new ticket being more expensive. It follows by implication that in the event that the new ticket is cheaper, you should be refunded the difference.

However, the SAA makes it almost impossible to find a flight that's not a lot more expensive, claiming that there are no tickets available in your class for months ahead. Yet you can easily find these tickets on their online booking system. Nonetheless we persisted until we found flights cheaper than the original. Then they claimed that in the event of the new flights being cheaper, they do not reimburse the difference. Not only is this illogical, but it's not at all supported by their own terms and conditions.