Demand for hefty Registration processing fees of Rs.29000/-

Dear Sir, I had purchased a flat of 1250 sq ft area in Merlin Basundhara project in Behala. I have paid all the installment. Now during registration they are demanding Rs 29000/- extra as Registration processing fees. This is in addition to the Govt Registration fees which comes around Rs.150,000/-. Now my question is can they demand such high amount of Rs.29000/ extra as Registration processing fees? There is no mention of Registration processing fees in the agreement signed by us. But there is mention of incidental charges. When we booked the flat their sales representative said that this incidental charges can be at best Rs. 3000/- to 5000/-. Now they are referring to this clause of incidental charges as the basis for Rs.29000/- extra. Is it justified and legally correct? Moreover they are insisting to complete the registration process in their office not in any court. My bank, SBI,RACPC Kolkata from where i have taken loan has also reservation in sending their personnel to their office. They are ready to go to court but not in their office. I have requested MERLIN to do the registration in court and i am ready appoint lawyer and bear other related expenses for the registration process but they are not agreeing. Now what I can or should do? Debashis Paul E Mail: dp8865@gmail.com mob:9434792242