Ready to check in & board, client refused

Good day<br> <br> My husband, Mr R Sivrathan was booked through his company travel agent, to fly from CPT to JHB on Friday, 18 March 2016. The flight was booked for 8h40 the morning. Mr Sivrathan arrived to check in and borad at approximately 8h10. He was turned away, and told that because he was not checked in exactly 40 minutes prior to flight, that his seat was sold to someone else!<br> <br> This is unacceptable. The reason for the flight was to meet the director of the company he worked for. <br> <br> Mr Sivrathan was forced to book with another airline on the spot in order to attend the meeting, which resulted in money loss of R5600.00 and still this made him 90 minutes late.<br> <br> We are not happy at all. How is it possible that a airline can sell and benefit from the same seat twice?<br> <br> I would like the CEO of this airline to contact me ASAP.<br> <br> Mr. Sivrahan travels often via Kulula / Mango, never once ever having a issue.<br> <br> I will be contacting whoever needed, who ever regulates airlines, but you will hear from us again!<br> Mrs Sivrathan