Incorrect Settlement Amount

I phoned in at the end of October to their call centre to request a settlement amount which they sent. I made full payment by the 29th of October and my account was settled as per the reflecting statement.

Now they are calling me to request further interest for the month of November. One of their Call centre supervisors informed me that they made a mistake and will write off the amount as the error was on their side, yet I keep getting calls from them requesting payment.