Does not pay as per Authorization

I have phoned discovery for authorization for my sons drip at Eugene Marais hospital. I gave them the icd 10 codes and the procedure coded I was told that its has been approved and all will be paid from my hospital benefit.<br> As my surprise none of it has been paid for and I need to pay it. I phoned discovery and they told me that unfortunately they don't pay for that procedure and I will need to pay the hospital from my own pocket. So what did they actually authorise and why do I have the authorisation number. This is not the first time this happens with me with Discovery and after a long battle the previous time they paid as it was a problem on their side