High levels of incompetence demonstrated by Unisa Library employees

I loaned a book from Unisa Library Services on 16 August 2019. It was, apparently delivered at the Osizweni Post Office, long after the submission date of the assignment I needed it for. Since there was no longer a need for it, I requested the Post Office to return it to Unisa. A few weeks down the line, I was informed that I have not returned the book and I therefore owe them. I went to the office and they showed me a register indicating that the book was sent back to Unisa. I've even made several visits to the Main campus and I was told not to worry, they'll sort out the matter. Today it's 02 March 2021 and I'm still getting emails informing me that I owe library fees. This is between Unisa and the Post Office and has nothing to do with me. I never even saw what this book looks like and yet I am being blamed for the incompetence of both the Unisa and Post Office staff. I can't even register for the few remaining modules as I am blocked for owing library fees. I tried calling in several times, they're not answering their phones. Such level of incompetence! I'm so disappointed in Unisa. Can't wait to finish off and that would be the last time I enroll for any programne with them