Withholding documents

I have been waiting for 10 years to get my Diploma. I have all other certificates and I even have my marks certificate which is stamped by the college. I missed my graduation due to working shifts and weekends and when I did go to the college to collect my diploma they told me they mis placed it and cannot find it. Then I went back a few months later and the excuse was I owed some money still. That is not possible because they would of held back all my certificates if that was the case. I really need my diploma because I am immigrating. The service I have received is ridiculous. It has been a tiresome fight and struggle to get a piece of paper. It cannot be that difficult. I need this sorted ASAP.