Bank delaying issue related to bank locker how to proceed legally

Hello sir, i am shruti. i had kept my jwellery the next day of my marriage in the bank locker in the name of my husband's grandmother (she was no more at that time). none of the bank employees or manager of that bank informed us about the consequences of using the bank locker of a decesed person. we have operated the locker for two times after that, through my husband's mother. the third time when we went to operate the locker, the bank staff stopped us from using the locker and asked us to bring the letter of authorisation by legal heirs (authorising my mother in law to operate the locker) duly attested by the village officer which was done. but still the bank is taking about legal procedures and delaying the issue without proper answers. what is the legal way to get back my ornament?. can we move against the bank as they supported us in operating the locker initially?