nominated gp does not get paid for consultations

i am on flexifed 1, where i can choose a GP that even if my medical savings is depleted they pay the arranged consultation fee. So i go only to this nominated GP. What a shock when i received an invoice for almost 6000 what my medical aid have not even paid consultation fees tge past few months. so now my gap cover do not want to settle as my medical aid did not pay and they pay short payments