I have been flying DONE5 ex JNB for many years all issued by AA and the back half of each trip interestingly are all QF sectors and other than on one occasion all have been reissued by AA with NO service fees as the changes were date changes only.... whilst on one occasion I bypassed AA and used QF who were a pain to deal with until I managed to get hold of a fabulous senior supervisor who told me "to go to sleep and I will fix up all your sectors and email you the new eticket "...which happened overnight with no charges but was reissued on QF stock....will always use AA I think to change dates as I think its a safer way to go