Back in December I booked a DONE5 business class out of Johannesburg on Qantas. I couldn't pay for it online for some reason, so I called the local Qantas office (in Tokyo) and they sent an email to the Joburg office with my credit card details, and half a day later I got a confirmation email from Joburg and I was good to go.

Since then I've needed to change dates on my flights at least 5 times, and it hasn't cost a thing. I didn't feel like asking directly, but after talking to them so many times it came out that on biz class they don't charge for date changes (they do on economy) but they still charge for routing changes - US$125 each time they have to redo the ticket, which can include as many changes as you want in one go.