mone taken out of account

I am writing on behalf of my friend...her husband passed away and her husband family went to Absa bank in main street Johannesburg and withdraw a large some of money from her husbands account and they used an affidavit that they got from the police station.The wife did not know about it until she went to the branch with the power of attorney she got from the court.She would like to lay a complaint against that branch what must she do. She can be contacted on the following no *** Carmen is her name. Thank you