Charging me double

I gave them my banking details for debit order, they never use it, so I always pay online by myself. Today they debit my account on the 3rd after we agreed on the last day of the month. They say I owe debit order reject fees but I already paid they installment online.

They are making money by debit order reject fees. Please I don't have time for this nonsense, I paid you already, the payment reference is 020824JAM0101