*********** with accounts and have no clue with cs

I was admitted at Netcare waterfall city on the 28-Jan-15 and my medical aid authorized the procedure to be done in hospital, and I was discharge 3days later the 31-Jan-15 . On the 06-Aug-15 I received the call from Regina Mamabolo she said there is a R11820.00 that the medical aid didn't pay I ask her why 6months later that she bring that up she pushed the blame to the case manager that she didn't authorize for that day but Bonitas paid the account thou it was a stale claim .Today the 30-Sep-15 the same Regina character calls me and tell me that I owe the hospital R274.65 it was short paid by the medical aid on the 28-Jan . I ask her why she is telling me now the time she was following up on R11820 didn't she notice that there is a R274.65 that is outstanding she said she doesn't answer to me I must pay them then when I ask to speak to her manager she hung up on me, I return the call she hangs up again. She only sent me the 1st sms reminder I am not responsible for Netcare who hire people who doesn't know to work on accounts that treat their patients with no respect and give them bad attitude