Paid up letter and they don't stop debiting money

I have been paying MBD for 6 to 7months I even arranged a debit order. They called me September 2022 saying on the 8th of October they will Debit the last amount and they will send me my paid up letter on the 15th. I waited on the 5th of November I received an SMS saying I should have sufficient funds in my account they will debit on the 8th of November I called them asking how is that possible because I settled the amount I owed them last month the lady who was assisting me said the balance shows that I don't owe them but they need to debit an amount before they can close it . Where does that amount come from if my balance is zero and why Is it my fault that they didn't close my account. MBD is a **** they **** people money