For my own ticket, after a lot of fruitless emails to S African couriers, I finally came across Postnet South Africa. I was able to fill out a web form (& pay by credit card) & my ticket was picked up from Cindy the next day (& subsequently delivered to me in Europe a couple of days later).

You don't get online tracking, but the price (about US$ 46.00) was only about half that of FedEx, who wouldn't reply to my emails in any case.

I also found that the email support from Postnet wasn't up to much, and their phone no. is a non-geographic S.African no. that wasn't accessible through Skype. After some guessing, I worked out that their main no. is +27 11 207 2900, if that is any help.

For a CPT-JNB (or CPT-Oz?), I'm sure they would do what you need. If you need a same-day pickup, I'd suggest doing this early in their day, as they have a lunchtime cut-off. (From Oz, that should be pretty simple.)