Installment not debited

They didn’t deduct their installment on the 25th and kept sending emails that my card is blocked or have insufficient funds yet all my debit orders went through even the month end ones. Tried to pay manually online and it gave me issues that my password or login details were incorrect. Sent them several emails with a response that my query is resolved and closed without associating with me. They keep adding daily interest on the installment that they cannot debit on their side due to their own failed systems. Now they want me to pay the full amount with interest. I’ve taken the legal route and will contact Ombudsman if necessary.