Resale of a property.

Hi Sir, I am in a strange situation, I bought a flat in vashi which was under-construction in 2010, I paid builder 20% of agreement and 80% availed loan. Bank had released 80% of the loan amount to the builder and held back 20% of the loan amount and asked builder to produce all the documents and send a demand letter to the bank to release the balance approved loan amount (20%). In 2012 builder received OC for the building and didn't not inform any of the flat owners about the same. I had rented that place so didn't took much interest about it. Now I wanted to resell the flat, when I reached bank to know my loan closure amount they informed that builder has not sent a demand letter yet for the amount held by us, also the OC copy is not submitted by builder. I tried getting in touch with builder but he changed his office the only mode of contacting is his mobile number. He is not showing interest meeting up personally also demanding the amount held by bank in cash from me. He told me he is not able to give any receipt for any such transaction. Somehow I got OC copy from NMMC office. Can I resell my flat, I am ready to pay builder the amount held in bank through cheque but he is not accepting the same also he is not ready to share any of his address where he can be met in person.