Product: Money transfer, virtual currency, or money service

I am filing a formal complaint on EastWest Bank ( the EastWest ), who myself and my mother have a joint savings account with of which my sister has our solely permission to help manage the account while we are residing abroad. 

In XX/XX/XXXX, while reviewing our bank account online, we discovered that our account had three unauthorized debits ( the Transactions ) that seemed to have been made electronically without any 2-step verification process as any other of our transactions : XXXX. XX/XX/XXXX in the amount of {$9500.00} XXXX. XX/XX/XXXX in the amount of {$500.00} XXXX. XX/XX/XXXX in the amount of {$7500.00} It turns out the recipient of these three transactions was listed as my sister name to an unknown bank to our knowledge called XXXX XXXX XXXX XXXX XXXX XXXX XXXX We immediately contacted our bank and an investigation was finally putting in placed in XX/XX/XXXX along with our notarized ID Theft Affidavit. EastWest replied on XX/XX/XXXX and determined that the transaction was made with the same IP address as ones previous authorized transaction that my sister made within the same account. EastWest concluded that no fraud has been found and was able to recover {$3100.00} from XXXX XXXX at the same time and closed the case.

We then contacted EastWest several time sin between XX/XX/XXXX and XX/XX/XXXX to discuss this matter and requested for a deeper investigation. We found it strange that if there was no fraud occur, why would EastWest take action and would blindly partially recover the money for us? We also asked the bank to called XXXX XXXX  to joint investigate the case and gave EastWest the permission with my sisters SSN under her consent to proof that she has never open any account with XXXX XXXX. We were asked to filed a police report to attached with the letter we send to EastWest in XX/XX/XXXX requesting to reopen the case. 

On XX/XX/XXXX, the bank respond and still insist with the same conclusion that there were no error found. We responded back to EastWest and asked them to provide us with the proof of same IP address was used. The first document that EastWest provided did actually shows a different IP address was used for one of the fraud transaction. After we challenged EastWest, they modified the report and provide us with a second version which shows the same IP address was used. Which made us doubt EastWest investigation credibility into our claim. 

We took further steps and contacted XXXX XXXX  ourselves in XXXX XXXX along with my sister SSN under her consent. Which XXXX XXXX determined that my sister has never opened an account with them ever before. The XXXX XXXX suggest us that EastWest should call them to verify this and which was normal for banks to do such action all the time. However, EastWest refused to do so as they sees the case was closed.

We found it incredibly unprofessional and insulting that EastWest refused to take extra steps to help us, their customer for decades. We are complaining that EastWest Bank practices when it come to their customers report of fraud and the lack of security provided to their customer. We felt extremely insulted as a victim who where claimed to be a criminal. The bank was naive and ignorant enough to determined such case was not a fraud action based on the same IP address was used where companies all over the world are getting hacked and hackers are sophisticated enough to mirror IP address to conducting such crime.