on joburg special rules frequency for air to air position reports..."Uh,all statio-io-io-ns,th-th-th-is i-i-is A-A-A B-B-B C-C-C, (lady pilot stuttering uncontrollably)...then another (male) voice comes up "oh ****** it this is -ABC,C172 Coming up the eastern shore of Hartebeesport dam approx 7000 ft heading southbound...THE WIERD THING IS THAT THE MALE VOICE WAS FROM ANOTHER PLANE! obviously he was fed up with the stuttering, had the a/c in sight and decided to report for them!