Incorrect account debited

I changed my banking details. In December. I calledCell C to inform them of the changes. I provided them with the correct bank account number with the acb code. They proceeded to debit the WRONG account on my 2 other contracts.. I have done manuel payments in Jan, Feb and March. Dalmarie informed me that all the debits went through via debit order. (Which is a lie That means I hace been debited twice. Now who is going to pay for thd unpaid fees which when they debited fron the incorrect account. Delmarie informed me they are not at fault