Cancellation of Loan Mortgage in TCT

My friend and I are both property consultant and never been a licensed broker because we are not reach college education and don't have a required units to file in the PRC for a licensed broker. Our problem with this property that we deal are no cancellation annotated in the TCT because the Credit Corporation is no longer in operation and that their status in SEC already revoked. The owner of the almost 5 hectare agricultural land is already dead and the heirs which are the children are now wants to sell it to anybody. The only problem is the TCT don't have annotations indicating that the loan mortgage was already been fully paid. We already asking the PDIC to help us this problem because the agreement between the owner and the Credit Corporation was already lost and the receipt and other documents is nowhere to be found. Should we go to the Registry of Deeds to fixed this? Hope you can help us solve this problem. The Transfer Certificate of Title was already in the hands of the heirs and they want this lot to sell in a reasonable price. Thank you very much!