Settling their scores by targeting those who resigned

I have resigned in March 2023 & I was told I owe bursary & days ro the amount of + 10 000 which was concluded by HR & Finance Directorates. I was requested ro sign the debt form with such amount which was also sent to GEPF so that it can be deducted from my pension pay out. The amount was indeed payed but to my surprise I received an email from PhithiSe@dsd.gov.za that am owing bursary interest of 582. How can one settle debt & 11 months down the line they say you still owe money. I mean they are the ones who calculated the amount & now they come back & say it was wrongly calculated. Phuthi told me GEPF cannot assist me in this regard. Yes my view also because they paid what was due to the Department. I paid & in no mind of paying any money because I paid for what I signed for not interest accrued after 11 months of resignation