Purchased morgaged property

I purchased a morgaged property,directly from the seller. He showed an application to sell the property,which had bank manager's sign and stamp. I made complete payment to him and the sale deed was executed. But now bank has declared his account as npa and is about to auction the property. Property is located in ghaziabad but sellers bank and his firm is located in delhi Where should i file the case and how can i get stay order against the auction.