Add sur name in bank account

Sir, 

My Name is Full Name is Vijay Kumar Bhati. I have open one saving bank account in SBI Bank. At the time of opening bank account I have submit by Votor Card for as proof of Identity. In My Votor Card my name is Vijay Kumar. 

Now, I would like to add my surname name in my bank account in SBI. 

What is the procedure & what formalities is required for addtion of surname in bank account. 

Regards 

Vijay Kumar Bhati