If I may suggest, perhaps you might try corresponding with an agent (or even directly with airlines) in RSA. IIRC, all calls to BA in RSA are redirected to COMAIR, so that might not be the best option... but if you can handle the phone charges to RSA, try the Qantas phone line in Jo'burg after 5.30pm, and you'll get redirected to the call centre in Australia for free. IME the QF agents are MUCH more familiar with the OWE rules than the Comair agents (or even the BA agents that I've come across).

Also, there's a QF agent in Windhoek (I forget which street its on, but IIRC its in the same building as the TAAG (Angolan Airlines) office, if you know where that is. I'm doubt you'll have much luck booking your ticket through that office, as they likely won't be any more familiar with the OWE rules than the Comair office, but if you organise your booking via the QF phone line in Jo'burg, you could organise to collect and pay for your ticket at the office in downtown WDH.