College refuse to refund caution deposit full amount

Sir, i have completed my B.com from a self financing college. Now i had completed my course and when i go to collect my TC and Caution Deposit which i was paid at the time of taking admission of Rs.1000. Now the management told that they will refund only Rs.300. They told us that the college is collecting a Comman fine from every students of Rs. 500 and They will deduct Rs. 200 for allumini fees also... But the management is not saying details about the comman fine of Rs. 500, they are deduct Rs.700 from each every students by saying Comman fine and Allumini fees. In our college their is around 2000+ students and they will deduct Rs.700 from Caution Deposit of each students.... Is their any rule for college to take 50% caution deposit as Comman fine from every student??? And the college is not ready to explain about the Comman fine too... Is it compelsery for every student to pay Alumini fees Rs. 200??? If college collects 500rs from eacj students.. they will get Rs.1000000 from students by collecting a comman fine.. What is this common fine? Is their any rule for management to collect common fine from each and every student... ? Can i handle this legally? Can i file a Complaint against this? How can we get our caution deposit back?