National grid sent me a notice over the summer sta...

National grid sent me a notice over the summer stating that they made an error and so a payment was not put through and it showed poorly on my account I've had to speak to these people 3 times on the phone to try to clear this up the last customer service representative I just spoke to said that she is not acknowledgingly that period because of their error they had me on a cash only payment. I made a payment on October 3rd the payment went through I have a confirmation number and I've had to spend 2 more calls stating this to the customer service rep who told me that it was my fault that they were not responsible for in any way shape or form. I spoke to a customer service rep named Barbara who says I am not acknowledgingly you or this problem.