Extremely bad customer service, the supervisor Bia...

Extremely bad customer service, the supervisor Bianca was very rude after I had made an overpayment on my account and did not want to refund my money! Its close to Christmas time I made an honest mistake by paying my light bill fee instead of my water utility bill. They want to keep my overpayment as credit!! I have been a customer for 18 years +, always make my payment on time and this is how they treat their customers?!?!?