malpractice and ********* behavior and constant harassment

I have no had an issue with FinChoice until the end of my agreement. I made the final payment due on my account in October 2024 prior to this there were no "system glitches" as their consultants called it. My final payment was reversed without my knowledge or any communication being made to me by FinChoice notifying me of this error. I had been making manual payments towards the end as I changed over banks and no longer used my prior account. I contacted FinChoice in which they said manual payments can be made as they dont currently work with Discovery Bank. They had processed the refund but kept their admin and interest fees to my old account in which I no longer have access to. I contacted their team as I was being harassed by the service agents stating I have defaulted and not made any payments. During these phones calls the support agents acknowledged that the payment was made but the system has issued a refund due to it being too close to the debit order date however this was never an issue in any other prior months but however became an issue only on the final payment to settle the account. I was then told it is not their responsibility to cancel the refund and I need to contact my previous bank for that refund. I stated I had no access to this account. The following month I again paid them the settlement and the same issue has happened. I have laid a report against FinChoice with the Ombudsman and I will be going down the legal route due to their malpractice and ********* behavior and constant harassment by their support agents.