Mr bkshres
you should complain this to US Embassy in KTM.
email this: ConsKtm@state.gov its a US Embassy Consulate e-mail that I have used in past to deal with posers.

They will reply you also. Explain in detail.

ConsKtm@state.gov
Consular Section
U.S.Embassy
Kathmandu, Nepal
Phones: 977-1-444-5577
Fax: 977-1-444-4981

Also you can Complain through US State Govt. web site. Nabil Bank should be kicked out to teach some lessons.
Let us know, how your complain goes..

thanks