Discovery medical aid doesn't give responses why some doctor was not paid.

I'm so disappointed with discovery medical Aid.. I gave birth last year in May at an authorized hospital. Discovery did not pay the full bill to the doctor, I have made queries about the account since last year but nothing has been done. I even 2 weeks back for the same query I was advised that they will investigate and come back to me. Till today I haven't heard anything from discovery yet I pay my premium every month but the service is pathetic.