FNB YOU DISSIPIONTED ME IN ALL THE YEARS

i have been banking with First National Bank for 25 years never ever changed my bank account never ever even thought about it. I even convinced my friends and family to move their accounts to FNB becayse i was a proud FNBer. My Mom worked for FNB for 35 years my Aunt worked for FNB for over 20 years and i also worked for FNB for almost 20 years but Yesterday FNB made a fool of me and i can tell you i have lost my ability to ever support FNB again. I am closing my account and i will make sure everyone i know do the same. this is my story. i gave my partner of 10 years ago signing authority on my account but we broke up and i never saw her again. yesterday i check my account and R2000 of my account with the REF STAFF. I contact the bank they tell me i did the transfer to a Miss Fourie and asked that they could do nothing i have to get my money back from her. i mean how did this happen? phoned her sister that i still talk to and she explained that my ex went to open a fnb account yesterday and after that she had 2000 rand in her account and she also has a staff account. how in this world does this happen? i need to get an answer on this matter how this was done?