Time Barred

In March 2011 took a home loan of 20 lacs loan for under construction home(flat in a builder project approved by HDFC) from HDFC. Paid Interest of about 9 lacs till March 2016. Builder company did not deliver and during investigations found that the builder company did not have requisite license in its name nor the title of land. We enquired HDFC about due diligence done, no response from HDFC. Then we filed a case with State Consumer Court, New Delhi in November 2016. During the pendency of the case in the said consumer court, on 29 July 2017 we received a legal notice from HDFC asking immediate payment of outstanding EMI with additional interest. We responded that our case is sub judice, however, willing to deposit the amount in any court/body designated by court or the advocate. No response from HDFC after that. Our Consumer Case is still in progress. However, we have received a notice for Pre-institution mediation for District Legal Services Authority. We have ample evidence that HDFC Ltd. did not do proper due diligence. Builder company is now under NCLT going through Interim Resolution Process and we have not received delivery of the flat. What should we do?