You ring the DWP helpline. Just be warned, when you do that they frequently try to push you into making your Mandatory Reconsideration request there and then on the phone. In your situation I would say that you are not in a position to make your request until you have read the PA4. But they can be very pushy!
Catherine
Nothing on this board constitutes legal advice - always consult a professional about specific problems
The following user(s) said Thank You: lesley, Dellilah