Bank is not giving account balance after account holder death

Myself Amit Mittal from Mathura,U.P. My divorced sister and her daughter lives with me since 2008. She died in January 2020. In her axis bank account, her minor daughter is nominee & I am appointee as guardian. In her registered will, she has given her assets & responsibility of her daughter to me. I requested bank to give a/c balance to me. I have given certified copy of registered will to bank but bank is delaying the matter from the day 1. First bank demanded probated will & now guardianship proof. I have visited bank branch many times. Everytime they returned me & are not giving their cause of rejection in writing. Somebody told me that in case of registered will, there is no need of probated but bank is not ready to listen anything. Now bank talking behaviour is also changed. They are ignoring my calls, my what's app messages. When I go to branch, treated me rudely. I have e mailed the full matter to branch, nodal, circle nodal and principal nodal mail id one week ago but no reply mail received yet. Please help me