For ex-SA itineraries, the online tool usually works OK for itineraries beginning with BA, CX or QF. It does not work for itineraries beginning with QR (and it tells you "please contact the airline" - good luck with that). For IB itineraries it been reported the tool fails right at the end - when entering your credit card details.

Historically people have preferred to book ex-SA itineraries with AA (and pay through its general sales agent there - Mindpearl). This is because AA has tended to have lower surcharges and it has been easier to deal with when wanting to make changes during the life of the ticket. But AA is now imposing a new policy that requires an SA billing address on the credit card used (this is not part of the rules and is essentially an arbitrary policy imposed by AA).