labor law.......

can a company force employees to cut there hours because they claim that the store is not making profits?? they are forcing full time workers to leave an hour early or and hour late or to take extended lunches to accomodate there business, but people that are contracted full time are not getting there 40hours a week pay. is this legal??? when I was hire there was nothing in the contract that stated that hours would be cut to acomodate business profits to their advantage and of course it had to be Walmart.