Account dispute and no evidence provided

I was admitted last year for allergies and the dr recommended a certain injection as the allergies were recurrent but we couldn’t determine what i was reacting to. On the day of admission, the Drs assistant completed forms indicating details of the injection and the whole assessment, which i took with to the hospital (Medi-clinic Midstream). On arrival, my medical aid was called to get authorization for my admission etc. the injection was administered and I haven’t had allergies. Fast forward about 2 months later I’m informed by my medical aid that the medicine is an exclusion and therefore was not paid. I have no problem with that, but my question was we knew when i was admitted and authorization was granted, why was i not informed then? My medical aid said that they were only made aware of the medication days after i was already discharged. I went back to the hospital and the hospital via email communication with David Mdluli who informed me that the medical approved the medicine on the date of admission but then pended it the following morning. They followed up and it was approved. I have requested this evidence so that i can provide to the medical aid as they are maintaining that the authorization was requested late. To this date i have not received that evidence yet I’m being harassed by debt collectors as they handed over my debt. How do they handover when I’m still disputing and they have not given me satisfactory evidence i requested?