Unable to get Response from DWP/PIP

Thank you all for your replies, I apologise that Ive not got back to you before, been a bit fragile since I had my 3rd Covid Jab. I did write to the DWP to the address on the form, as I had not had a reply I sent a further letter to them (Recorded Delivery) including a copy of the original. I nor my son has heard anything other than received a letter stating his benefit has ceased. I also drew to the DWPs attention that the original request from DWP stated that the form had to be returned by 30th September 2021 "or they are notified as to the reasons why it has not." I will keep you informed Thanks.

Just thought I would update on the current situation. I did contact the DWP by phone and explained the situation in accordance with their instruction of the Review Form. The next thing that occurred was they stopped his payment completely. I then wrote to them (recorded delivery) explaining the matter. No reply at all.
I then managed to talk to Darren at DHS who said he was aware of the matter and my letters, and he would send out a copy of the form. That never happened, so I contacted them again and spoke with Hayley, she to was aware of the situation , but was not in a position to send out a form, it had to be done by the case worker, as it was being seen as a Mandatory Reconsideration. Eventually she informed me that she hd spoke with the Case Manager and would be sending out a form that day.
That form never materialised.
But a week later his benefit was restored with no explanation.
These people appear to have little intelligence and are unable to make a simple decision. No wonder the DWP is such a mess.