SA British Airways ****!

Complaint Ref.: ***7 Booked a flight for my son from SA to the Uk. R14000 plus was the ticket. I then upgraded his seat with R4600 to ensure he received a spacious seat with enough leg space. I could not book a seat before check-in online. 24 hours before flight date I used the online check-in option and there were no seats to choose from? BA allocated a seat to him? So. My question is: what did I pay for? We received absolutely nothing fir R4600.00? I want a refund. Received no reply to my complain and their complaint system is archaïsch and unfriendly with limited options to give a detailed complaint! Not on! Mot acceptable! ****! JUSEF2.