If you actually had a written contract of sale with the bank, it is illegal: a contract is binding and enforceable. If there was such a contract and the sale has not gone through yet, you can sue for a court order blocking the sale and forcing the bank to sell to you (retain an attorney to help you; suing for a court order, especially on an "emergent" or urget basis (since you need it fast, before the sale occurs) is procedurally complex). If the sale has already occurred, you can sue for monetary compensation such as the difference in price between what you were going to buy this house for and what it would cost to get a comparable house in that area other than through a bank sale.