CAN SOMEONE PLEASE HELP ME URGENTLY? PLEASE!?

I KNEW THERE WAS A REASON WHY I HATE THIS BANK AND THEY JUST PROVED IT BY SINKING TO A NEW LOW. They are inefficient, unsympathetic and just downright disgusting and useless. I called on my mum's behalf , she banks with them for YEARS, but is struggling with dementia for A WHILE NOW. As her only daughter, i have been assisting her with EVERYTHING including her medical conditions , and also her banking etc. I logged into her account today and found a huge suspicious transaction that she could NEVER have made. Some international card purchase .CLEARLY this is *****. It sent her account into a huge overdraft which she doesn't even have, so how the transaction was allowed to go through its beyond all understanding. Its is now creating the impression that she owes this useless bank this money ????Meaning they will just take her pension for MONTHS with NO conscience whatsoever??? HOW the transaction didn't raise an alarm or didn't even generate a notification is saying to me that someone INSIDE the bank has tried to rob or **** my sickly, elderly Mother , and that's DISGUSTING to say the LEAST. I tried calling to get the bottom of it , they REFUSED to help me even though i explained my Mum isn't really aware of ANYTHING due to her mental health and that i am the ONLY one that helps her, STILL the agent is FIRST ASKING IF HE CAN TALK TO HER???? THEN , TELLING me to take a frail , anxious , sometimes confused, mentally challenged elderly person to a BRANCH where she must FIRST talk to the branch manager and THEN they will help me. I DONT understand how they could be SO cold and unwilling to assist . It broke my heart to think that they could have helped me within minutes but still chose TO JUST BRUSH ME OFF .. Does ANYONE that works there actually care for their elderly customers who have been loyal to them for YEARS ??