How to get bank letter for signature change in passport?

Why do you want a bank letter for changing the signature on your passport? The following is the procedure to be adopted for changing the signature on your passport.
You have to make an application for a new passport. You have to apply online for the passport and you have to fix your appointment to go to the nearest passport seva kendra.
You have to append your old signature as well as the new signature on the 2nd page of the passport application. You have to go to the passport seva Kendra as per the date and time of the appointment. You have to carry your existing passport, 4 Passport size photographs and a printout of the application with you.
In this process, they don't require any bank letter.
You have to carry your Adhaar card or PAN card. If you want to produce your bank statement as your address proof, you have to ask for your bank statement in your bank. You can give a normal request letter to the branch manager asking for a bank statement. You have to mention the period for which you want the statement in the letter you are giving to your branch manager.