Claim not paid without a valid reason

Tshiamiso Trust employees provides very poor service, my dad who worked at Harmony mine for more than 20years and later retired due to medical condition called Silicosis, exit medical certificate was issued and he was advised to submit a claim till today we have been struggling and suddenly we are being told that he never had lung infection or TB therefore his claim was declined. How is this possible, why was the medical certificate issued. We tried to dispute and no one attended to our matter. I need the matter resolved and contact me on dineoprumoleko@gmail.com