CHANGE OF BANKING DETAILS

I have been trying to change my banking details for the debit order for the past 3 months now, and every time i call in i am told that it hasn't been changed and the consultants did not make notes on the system. Every time a debit order bounces i have to pay the penalty for something that is not my fault. Clearly your system are are problem and you don't even bother to check what the problem could be. I am not willing to pay any penalty because of your system or staff error. Please sort this out!!!! My line is going to be cut out tomorrow, and i cannot afford that to happen!!!