Asking for more fees

Sir i have taken admission in T.I.M.E. (a educational institution for preparation) in cannaught place (new delhi) to prepare for my cat exams. I took admission in january 2014 by making a fees payment of 40,139 and started my classes in mid of january. but my mid of march i realised that there is too much pressure of cat studies so i decided not to pursue it furter. i talked to authorities for transferring me to cat 2015 batch.. they agreed . they explain me the deduction of 16000 out of 40139 from the fees. on my continuous mail to them they failed to explain me how the deduction of 16000 took place. instead they are asking me more payment of 26000 for transferring my batch from cat 14 to cat 15.. i have also asked them to give me in written the deduction of 16000 but they denied… not only this they have not returned me the rest of amount which is 24139 (40139-16000) they kept the 24139 with them instead of returning to me and also not providing any discount on cat 15 fees…….
they are not returning the amount rest with them after deduction nor giving me any discount on cat 15 fees instead they are asking me 26000 more for cat 15 fees… sir plzz help me…