Only 25000/- received against 51000/- booking amount almost after 8 months

Issue - No Refund of Full Booking amount after booking cancellation -14 May 2017 we had booked flat with booking amount 51000/- -In mid of September 2017 we had decided to cancel booking as we were not able to sale our existing property to buy this booked property. -According we had informed to builder the same via mail as well as personally on Oct 2017. -We had demanded refund of booking amount and they told us we made few expenses like paid taxes so we wont be able repay booking u amount. OR wait for some time till we get new customer for said booking cancelled flat. Many times we had visited builder office for booking amount cancellation but we always received unacceptable answers from builder side like 'sir is not in office' 'looks like its difficult to repay u' 'come after some days' etc. Me and my family memebers were got very frustated and this was really pathetic response we had. We had accepted cheque of rs 25000/- today . We are not happy what ahout we do. Please suggest!