Ots offered and deposited 25% of ots offer now refused

Sir, We have taken a CC loan of Rs.4.00 lacs (NPA) for our shop with mortgage a land in PNB and now shop is closed due to loss and bank offered OTS of Rs.1.50 lacs by showing the OTS documents and told to deposit 25% after signing this offer and the rest would be paid within 45 days. We paid 25% of OTS offer amount at the time of signing this offer and now branch refused to do OTS saying we couldn't initiate this offer because of mortgage of land, we will sell it. Sir we requested them that you offered the OTS and we have accepted it by depositing the initial amount of 25% and how you can refuse it. They told that by mistake it has been done by Circle office, if you will increase the amount of OTS then it would be settled. Sir, the OTS has offered by the Circle office directly to the branch and branch saying that they did a mistake. Sir they have not denied in writing. But we have a copy of OTS offer and we send a letter to the branch C.C. to circle office attaching the OTS offer letter with the payment proof to acknowledge the bank. Sir, we want to know what any legal action can we initiate as the bank offered the OTS and after our acceptance and deposited the 25% of offer amount can they refuse it by verbally saying that it was a mistake. Please advice....