Hospital shortfall

Please could if someone can please explain to me why if a Medical Doctor advises us that my wife must stay in hospital for a certain period, Discovery's authorization's deem it fit to undermine a medical Doctor and decide that she needed to stay in hospital for a shorter time. On Discovery paying the hospital they paid short and now we have to fork in the balance. Please explain, from when did Discovery employ medical doctors to run their authorizations department? To make matters worse, the doctor that treated her sent in a motivation for why she had to stay longer and still Discovery's authorizations still decline it. Why on earth do we have to pay these exorbitant prices for a medical aid and claim on their website that they cover 200% of a hospital stay and then just to have then only pay out a partial claim. Looking forward to a response.