Cancel my account

My account was supposed to be canceled on Jan 24 (I went to the store in person to cancel both mobile and home internet on Jan 12 and asked them to make a scheduled cancellation). And it still hasn't been cancelled until Feb 26. After contacting again, it was finally canceled. However, it wants me to charge for the whole month I didn't use, and it's not even my fault. I need this to be resolved. Since the account is already cancelled, I am no longer able to use the Xfinity support agent chat feature as well.