Need your valuable guidance

My parents are taken a property during 1992 in Bangalore. The property is well established and came under to BBMP. The land has been taken from Mr.A to Mr.B under GPA. Mr.B. has given the land to us which my parents have taken under GPA registration. Now we are trying to sell the land, but unable to sell the plot. Because the party is telling that it has not yet registered. As per my knowledge I enquired BBMP and they have informed that it has been done under GPA registration, you have obtain a new khata and extract. As per them, I have taken A Khata / extract / EC. I have also having the Xerox copies of old documents: A+B+C ……….D (ours). Now I have already applied for RTC/RR5/MR5 and other documents for our records. If I go to Mr. B he is not alive right now. Some persons are informing to get the signature from Mr.A and he is demanding a huge amount to come to the registration. As discussed with one of the provider, he informed again that this document is got GPA registered. Now you have register youself. He has informed me to pay the Government fees through DD, so that after pay the amount it will get registered to you and you can sell the land. Please let me know If I pay the amount to Government is it possible to get it registered on my name. Waiting for your valuable reply.