Money deducted from my account without my permission,

why would you guys allow people to get into our accounts and deduct money without out consent? i am very angry i was travelling and wanted to send money to my wife and i got an insufficient funds message when i know i had money in my account, when i check my transaction history i see an amount of R1 346.40 deducted from my account, why would my money be deducted without my permission, why do you give people permission to deduct my money? i want my money back and good explanation otherwise i am closing my account, my money is not safe at FNB.