Objective C, If: a button is not equal to (blank)

I need to figure out how to code an if statement for when a Button's title is NOT a certain string. I already know that to code for if a Button's title IS a certain string, it looks like this:

if ([topLEFT.titleLabel.text isEqualToString:@"Choose for X"])

But, simply changing the "isEqualToString" to "isNotEqualToString" will not work. What would a simple solution be?