For my sale bookings I have made multiple changes to flight dates/times online and offline without problems. I have also received the "error message" recorded by others and have caused my MMB change options to grey out. And now one of my bookings has completely vanished from the MMB list. I can still evoke it manually but I find it unsettling that it is now residing somewhere "out of sight".

On one occasion (offline) I had to pay more taxes - that was before the decrease in fuel levies - and the amount checked out with a dummy booking. (I checked because it was a suspiciously round amount!)

I can also report that for one of my bookings I changed my starting point and my final destination in two separate transactions - it was JNB-LHR-JNB and then CPT opened up, first for the return and then for the departure - without any consequences to the mileage required. Of course this was done via BAEC in Jo'burg so may not be a universally reliable precedent.

So to sum up my experiences:

• Neither online nor offline changes affected the number of miles required
• Taxes were recalculated (to my disadvantage) on one of the offline changes
• Changes to the departure city and final destination were accommodated without penalty
• The availability of the MMB button that allows changes has been very fluid - it comes and goes

My questions:

• Has anyone else had a reservation disappear off the MMB list after making changes? If so, does it ever come back?
• Has anyone received a refund of levies/taxes after making an online change? Is so, how long did it take?