Hard to say without having access to your account, which I don't have. Did you call (either your bank or Verizon) to cancel the payment? Were there sufficient funds in the account to make the payment? Could the information have been entered incorrectly and therefore the payment could not go through?
I'm just throwing some ideas out there, but it's really impossible to say without knowing more about your accounts - call Verizon Customer Service (800-922-0204) and they should be able to tell you what's going on.