I have been awaiting my refund from Rosebank college for over 1year 6months , they said I owed them money so I paid them and later found out that I was not supposed to pay the amount owed as my account was initially settled

I have been awaiting my refund from Rosebank college for over 1year 6months , they said I owed them money so I paid them and later found out that I was not supposed to pay the amount owed as my account was initially settled. Now they are telling me that I still owe them money even through they sent me my graduation letter, I am frustrated because I don't even know if I will be allowed permission to graduate