BA flouts the Consumer Protection Act

I booked a return flight on BA from Jhb to Durban (Ref PBDP6J) to run the Comrades marathon. The flights were Jhb-Dbn 9th June to return 11th June. I pre-booked a seat for the return leg.

I then decided to rather travel down to Durban on the Friday 8th June and as the cost of changing the ticket was more than booking a new ticket, I booked a new one-way flight (Ref OJMBI4).

When I tried to check in for my return flight, BA informed that as I had missed my first flight, my return flight has been cancelled! This despite the fact that the return flight had been booked and paid for and that a specific seat had been booked and paid for. I then needed to book a whole new flight for more than R2,500 to get back to Jhb!

Completely unacceptable and will definitely be the last time that I make use of British Airways - How can the return leg of a flight just be cancelled when it has been paid for.