Services purchased by authorised agent

Hello, please could you give advice.
If a person was to arrange a shipment of personal items from the USA to UK
on behalf or his parents, signed a U.S. contract as the owner / authorised agent for the move can you confirm if under legal terms he would be responsible for all payments obligations. Can he walk away from the debt on the contract? The understanding was by all parties that this is a shipment he was taking care of for his parents and which they own the goods. I need to determine if the son is legally responsible for any unpaid funds or his parents for whom he was acting ?
Can you clarify? We are looking go to court but his defence is that he was acting under his parent's direction and that although contract is signed by him as an agent, it is the parent we would take to court? All communications & payments were through him, not the parents. Legally what responsibility does the person signing contract as agent have?

[randalljd]

Normally he is responsible if it is owner/agent--and if he signed he is liable.

If he is under 18 he would not be liable.

File against all of them--the son and parents.