Claim Refused after obtaining authorisation

I was referred by my Doctor for an eye test.

I went onto the discovery app and found a networked optometrist which is allocated to my specific plan.

Upon arrival authorisation was obtained from Discovery by the optometrist.

The claim was rejected and the optometrist is in the process of handing me over to their attorneys.

I have raised this issue via the app (chat function) and a lady phoned me back and said they would provide me with a solution. I never heard back from them.

I raised this issue via email to *** but after 3 business days I have yet to receive a reply.

How does this work when authorisation is obtained and then the claim just gets refused and not paid.

This is not fair practice.