my credit card company did exactly the same to me, my payment was due on a saturday and they requested the money on the tuesday, this sent me overdrawn however i was lucky as i checked my balance on the wednesday noticed what had happened and rang my bank who then took the money back off the credit card company and put it back in my bank account, but the credit card company then cancelled the direct debit.
i also know someone who had the same thing happen but she was charged by her bank, she rang and complained to her credit card company who "as a good will gesture" took the �35 off her balance
I think a lot of these companies try and get their money early for god knows what reasons hoping people wont notice or wont complain, maybe my fsther in law is right when he starts his rants about not trusting big companies and not paying for anything by direct debit