need help on my bill

hi parents i am very very confused on my NUH bill firstly, i got a msg to pay $165.48 for my outstanding bill and then was told i have a credit bal of $1046, so i called up the billing dept and asked them to explain. then, she said i dont have to pay the $165.48 as it will be deducted from antenatal fees and regarding the credit bal, they will refund me after the finance side check and supposed to call me to explain the bill. so a week later which is today i check again the bill and suddenly the credit bal is missing....and nobody from their side called me to explain anything.... i thought i'm supposed to get a cheque back for that credit bal too.. pls help me i'm really confused. thank you