Medical bills not paid by Discovery medical aid.

I am not impressed by Discovery medical aid service. I already sent six emails to Discovery buy no one gets back to me. I keep on getting an automated responses which states that a consultant will get back to me since last year November until today. At Lancet they said they sent an invoice to my medical aid and it was part paid but when I called Discovery they said they never got that invoice, there is also another invoice when my son did a surgery that they have not paid and the one for the hospital admission. I don't know what to do anymore and I don't want to be handed over because of those outstanding medical bills. I am tired of buying airtime and wasting more money calling Lancet and Discovery. Please assist urgently!!!!!