Under valuation by bank peoplel

The bank's vlaued the property not even 50% of its actual value in the market before about 45 days and issued the sale-proclamation notice before about 20 days and it seems that their tougher attitude of them to finally setle the terms of sale-proclamtion.  

What are the apprpriate ways to stop them urgently and to proceed  further.

Regards

Thanks

HARIOM