We are sorry if the issue was not resolved to your expectations. We liaise with the takeaway on behalf of the customer when a food complaint arises and try to resolve it in the best way possible but the refund/compensation is authorised by the takeaway which would explain why the Live Chat agent was unable to offer you a refund as it would not have been approved by the takeaway.
Please try getting in touch with the takeaway to find out more about your refund rejection they can give you an explanation.