On your reference I will provide you HDFC Bank, Signature Change Form so that you can make changes easily.

Here is the application form

Signature Change Form



Here I have some more forms issued by them
Application Form - Education Loan
Application Form - Gold Loan
Gold Loan Renewal Authority Letter
Gold Loan -Email Margin Payment Form
Gold loan - Partial Payment Authority Letter
Gold Loan - Terms and conditions
Standing Instructions (SI) Mandate
Customer Request cum Acknowledgement Slip Form
Request for Shift in Due Date
Request for Special NOCs
Request for Intimation of Theft of Vehicle
Request for Cancellation of Loan
Request Form - Loan Against Securities for TRF (Annex. W)
ACH Mandate form
Business Debit Card application form for Trust,Club,Society,Association
Jet Privilege Debit Card Application form for HUF customers
Business Debit Card application form for Sole Proprietorship
BillPay and SI on DC Application Form
Jet Priviledge Debit Card Application form for Partnership, Private Ltd and Public Ltd
Jet Privilege Debit Card Application form for Individuals and Sole Proprietor
Business Debit Card application form for Partnership Pvt. Pub Ltd. Companies
Blocking ATM & Debit Card Form
Debit Card Pin Re-generation Form
ATM Complaint Form
Card Holder Dispute Form
Business Debit Card Application form for HUF

Address:-
HDFC Bank
1st Floor,C.S.No.6/242,
Senapati Bapat Marg,
Lower Parel,
Mumbai - 400 013.