regarding refund of caution money

Location/place: kolkata

Name of company/service: bengal institute of technology,kolkata

I got admitted to the engineering collage in Kolkata named Bengal institute of technology,kolkata in 2007.at the time of admission they took 15,000 as caution money.
now,more than 1 year has gone and they are refusing to return caution money.they are saying that in admission Receipt by mistake they wrote 15,000 as caution money.