Strange Letter re Assessment Decision

My adult son, who does not live with me, has mental health problems - has received Work Related ESA for several years.He attended re-assesment interview with me in October. In November he had phone call saying they would phone him next day about his assessment. He did not tell them he would not be there next day as had appointment at DWP. I attended that apointment with him. DWP staff said he should have stayed at home to take call and when they phone like this it usually means they are moving him onto JSA. However I knew he would not have answered the phone as he understandably was terrified (suffers from anxiety) but I did not tell them this.

End of November received letter headed "Your claim for Employment and Support Allowance" which said they had looked at his claim again and because of a decision on his capability to work he had been placed in the Work Related Activity Group and it gave details of the money he would receive (which same as was already getting).

Is this a new procedure - that they don't tell you how long you are in the group they place you in? or is there a missing letter? or can they suddenly out of the blue send him letter saying he is removed from ESA? Do moderators know? Perhaps I should phone and say there seems to be a letter missing - but am worried it might make theposition worse.

I know I can phone and ask for copy of the report of the person who interviewed him. Please tell me the phone number and what exactly do I ask for? Thank you. I really appreciate that this site helps so many people. Ella

Thank you Gordon. When he first went on ESA a long time ago (moved from income support) his letter said he would be on it for 2 years. He in fact was not called for re-assessment for over 3 years.
I did not realise 2 years is the longest you can be on WRAG without re-assessment.

However, I would still like to get the report of the Health Professional who interviewed him as it will help to know what this person said when he is called in again for the next assessment.
I know it is called an ESA 5 but what number do we ring to get a copy? Thank you in advance. Ella