Ticket selected, then when you get to payment OOPS

I just had to book a ticket for my husband, after getting quotes from all the airlines we selected the tickets for British Airways via [URL Removed] and got authorisation from his company in the DRC for the total amount and I proceeded to process the purchase of the ticket and went through each of the screens completing all the fields and by the time I get to press the final button to complete the payment, in a matter of a mere 5 minutes or even less, I get told Oops something went wrong with your booking and I need to call the call centre. I called only to be halfway through explaining to the first operator who said it is probably my browser when the phone gets cut off, so I called again and was told that message means the ticket is no longer available and was given to another passenger who booked at the same time and then I proceeded to hold for 5 minutes all whilst wasting my call charges when the message on your site could just have been more informative to speak to the supervisor Yazeed Waggie who was of no help saying oh sorry that's just how it is.