Regarding exam centre slot booking for NMAT exams

I want to report an error in NMAT booking slots in NMAT exam. The institute opened a re-registration window from 5th-10th Jan for appearing in NMAT exam. I have made the payment for the exam in the stipulated time (within 10th Jan). After the payment when we try to select test centre for the exam, it shows that no test centres are available and the customer support for this institute says that it is on First Come First Serve basis. When I asked how can I book test city, they say that all test centres availability is as per the website.(No centre is available currently). So I basically paid for an exam and I am not able to appear for the exam. It seems that they had kept the registration window open even after the seats were filled and still take money from applicants. When I asked them that I wanted refund, they told me that they won’t be able to refund me the money. I have raised a case in their website and they are telling me that this is some policy. Please assist.