Using Oyster - especially with the new punitive charges on people who do not touch in and touch out correctly - relies on a robust system for dealing with service disruption. If someone touches in and makes their way to the platform only to find the service suspended, they have the right to leave the station and continue their journey without losing money from their Oyster.
The system that is supposed to guarantee this is auto-completion/continuation. And that relies on Station Supervisors ringing auto number 1806, which relies on ... erm ... someone actually answering it.
Really, if you are going to introduce a system, at least make sure you have enough people employed to make it work in practice.