Hi cherrie, the benefits advisor service is back today. We don't talk to people, it's all online but my advice would be to ask for a mandatory reconsideration of the PIP decision. When you do that, think about what points you think your son should have scored, so you can explain why the decision is wrong. You can look at the points system here.
Insist on getting a written mandatory reconsideration notice. If that doesn't change the decision then please post again, or talk to a local advice agency. In the meantime as Sam says, you can talk to the Scope helpline for more information and support.