Wize Books ripped me off my money

On the 26th of July 2022, I sold 2 of my Financial Accounting textbooks to Wize Books. I bought them for R500 at Van Schaik Bookstore at the beginning of the second semester the previous year. Wize Books offered to sell them on my behalf for R370 and then take their R40 commission from the amount thus I will be receiving R330. I was told that the books were fast sellers so they could sell in more or less 24 hours. When I asked the cashier when I was going to receive my money they told me that I will be notified after my book is sold to come collect my money. I asked them several times to be precise on when I am going to receive my money and they continued to say that my books sold out fast as they were in demand so it wont take long. I signed a contract which stipulated the terms and conditions which I clearly understood. The contract clearly stated that after my books were sold I will be notified to come receive my money and that I am required to collect my money within 14 days from notification and should the time lapse I will forfeit my money. After 2 days, I went back to Wize Books to check if my books were sold as the cashier said that they sold out fast yet I was not notified. When I arrived to the store, I asked the cashier that was helping me prior if my book was sold and when am I going to receive my money. The cashier responded that the book was already sold but I have not been notified. I proceeded to ask the cashier when will I receive my money because its the beginning of the semester and I have to use the money to buy other textbooks and he said the I will receive it by the end of the semester which is around October/ November and unfortunately there is nothing they can do about it. I am not happy with how Wize Books have went about the situation because I did not have a Oral/ Written agreement with them that I will be receiving the amount art the end of the semester. I was told by the Manager that they will not change the process because of me, that is how is done to all the students. I could have sold them at a better prize as it was in an excellent condition. I was not informed of this situation and it was not stipulated on the contract.