Does discovery health know what they are doing

I had a CT scan & chest xrays which was authorized by discovery health. On the day I was told I had to pay R1500.00 as I was in my self payment gap & R580.00 for the chest xrays, I paid & got my receipt for R2080.00. I have sent these receipts twice to discovery. Today I was informed by discovery that I owe them R1013.55. (R1543.55 less R53.00). What is discovery doing. It seems they went and paid the R1543.55 to the service provider after I sent them the receipts informing them that I had paid. Can someone at discovery please sort out this mess they have created