Ithala negligence

My late mom was banking with them,when she passed away I went to let them know that she is no more,theya said I must come back with the letter of authority that was fine when I finally came back with it the money my mom left at the bank was deducted by Hollard and old mutual of which they also knew my mom was no more but they continue deduct the,when I asked Ithala why the account how come the account was accessible because I didn't get the valid answer