FlySafair take your money and don't deliver

I booked air tickets in March this year to Cape Town, and paid to reserve two seat numbers. On checking in, FlySafair placed both of us in different seats, and separated the two of us. What is the point of paying to reserve your seats then? Be very careful. Clearly, FlySafair will just take your money, and do not honour their side of the transaction. Furthermore, how does FlySafair make two seats available to others when the seats have been booked and paid for?