Okay, So I know we are using a Terminal and not a mobile device. Just pretend you are carrying it around with a really long extension cord. 
Here are my levels and their words.
EASY (Vending Machine)
Chips, Soda, Candy, Jerky, IAteYourDollar
MEDIUM (ATM)
Deposit, Transfer, Withdraw, Pay, GiveMeMyDebitCardBack
HARD (ARMORED TRUCK DOOR)
Wheels, Secure, Guard, Armed, KnockKnockGimmeMoneyPlease