Unpaid claims

I recently submitted 4 claims to Discovery to the value of R19,000 and only received R5,000 back from them. Reason - hospital not authorised. This is after I phoned Discovery before the operation to obtain pre-authorisation only to be told that I don't require pre-authorisation as the codes fall under dentistry. I have sent emails to the claims department and never get any response. I have also phoned and either get cut-off or end up waiting for close to 10 minutes before anyone picks up. I have spoken to two different people and both told me that I do not require pre-authorisation. Yet the claim is rejected because it was not authorised. ***?!?!?!?! Discovery is absolutely useless! Customer service is non existent!