Done3?
 

friend of mine has just finished a DONE4 and they said they paid for a done3, they flew cai-syd-(usa)-back to london,
with stops in australia, america and london . they were asking about changing the ticket to someplace other than cairo - i said dxb.
but on finding they paid (imho) the wrong price what would you do?
leave it? or go ahead and change , is it poss for a price increase?

she thinks it was because of the 1 flight to syd, but i thought this is not true.

If they paid for a DONE3 and went to Australia, then they indeed got a bargain and I'd be disinclined to tempt fate with an itinerary change, even if the "any place in the Middle East" rule applies. Someone at the tariff desk would need to figure taxes, and that might reveal the error. But the Oz=4 rule is so well known that I'd first examine the tix and make sure the price was actually for a DONE3.