Kulula's poor service

Kulula have a system whereby you can book a pre-paid seat. On two occasions in the past (flying from George) they have changed the airplane and what then happens is that all the pre booked and paid for seats gets automatically cancelled without a single communication to the passenger. You only find out once you start to check in or when you arrive at the airport. On both these occasions they did not even refund me for the extra money paid for the seats (R120 per seat for an exit seat). This again happened to me yesterday flying from Cape Town. Both myself and my wife's seats were cancelled and we were then allocated two different seats in two different rows. What is ironically, is that they can e-mail and sms you to notify you that you can now check in or that the flight is delayed ( which also happened yesterday), but they cannot e-mail or sms you to tell you that the plane has changed and that you now need to re-allocate your seat? I would also think that for the fact that you have booked a pre-paid seat, that they will take the effort to first accommodate you to the best of their abilities on the new airplane. To get a refund, you also need to specifically request it, it does not happen automatically.