Overcharging for car installments and *****

My boyfriends car installments have been coming off his account twice every month. There have also been transactions going off his account that he has not made as he is nowhere near the area of the transaction. The bank has no idea where the money for the second installment is going as it says car repayment. He has been into the bank multiple times and told the transactions will be reversed and its ***** etc but nothing ever happens. It is a lot of money and he cannot be expected to manage tge month with all of these extra transactions coming off his account. With other banks this would have been sorted out long ago and this is now the fourth month it has happened. This matter needs to be rectified as soon as possible. The service is pathetic