Security money

Hello, I'm aarti Last month i went to delhi to take coaching for upsc and hence i had to stay in a PG nearby. I finally got a room, paid one month rent (12000) +one time registration fee(around 5500) and made a security deposit of 12000. They got an agreement signed from me in which certain rules were mentioned like the agreement is valid for a period of eleven months, both the parties shall have right to serve one month advance notice for vacation of the room, and security will be returned at the time of vacation without charging any interest (which actually has not happened) etc.. Due to my ill health i couldn't stay there for long and decided back to return even before completing one month (6days were still left), and because of this medical issue i couldn't even give notice in advance. Upon asking for security money they started giving excuses and said once my room is rented then they will return my the amount or otherwise if it doesn't happens so, they will deduct money for each day from the date my one month period gets over.. somehow I managed to collect 6000rs from them rest they promised to return as per the condition...now the room has been rented to somebody else and they are completely denying from giving the back rest of the amount and are not even picking up the call ... This is not just the case with me ...but most of the other girls also. What should i do now? Please help me sort out this issue ..