Under Settings / Users, I discovered a "User" who was unknown to me and appeared to be from overseas. I would have liked to have cancelled this User asap but could not - it is Saturday. The Chat facility was of no use, so I finally rang and ended up with a person who could only handle Electricity accounts - I will have to call back on Monday. I don't know if there is an emergency service for this situation, but if there is it needs to be made available to customers. If not, there needs to be some alternative contact point.
The reason for accessing the App originally was to determine why my 100/20 account had slowed to 34/16 bps. I had received an SMS notice that there would be a closedown for maintenance on Thurs 11 pm and 5 am, and a follow-up advising the modification "had taken a little longer than expected....We'll send you another SMS with an update" (1:07 pm Friday).
No further SMS to date and I am operating at the abovementioned speeds.
Whilst I am annoyed, I am airing the experiences in order to find a constructive response from AGL and avoid the above issues repeating.