Consumer Redressal

Dear Sir, I booked a 3 BHK flat from ADOBE construction in Krishnapur Kolkata for 32.7L. I paid the total amount to builder as per agreement. During registration Builder gave me a bill of 1.2 lakh to pay for some charges which was not as per agreement and asked to pay another 65k to one of his employee as 2% commission. The registration got done but builder did not give me the key. Builder is still holding the key after 6 months of the registration of the flat. Need your help and guidence how to get possession of the flat. Thanks to all in advance for your kind advice and way to come out of this hurdle. Regards, Samar