try not to hit rigth left - use bit of tricky treat. assuming you have copy of the bank papers visit the Regional or Zonal HQ of the bank "not that branch" write a letter mentioning enclosures and request for verification as you are buying it from original leasee. get the letter received stamped, zonal / regional office may ask to goto branch & you can pull a lie that branch guided you to proper channel for Verification process.
once you have paper signed & stamped received wait 3 workings days or 5 and approach branch submit the same letter now addressed to branch head - get it signed & stamped received. 2 prong strategy will lead you to a result most likely in you favour. Either it will be proved that NOC was fake or original by the zonal / regional office / branch will give you complete details of outstanding due.
any short cuts and you will remain in SH ^^ IT