When laying out its subviews, a UIButton will set its titleLabel’s text value using its own title values, so that you can set up to four different strings for the four states (normal, highlighted, selected, disabled).
Because of this feature, setting the titleLabel’s text directly won’t persist, and will be reset by the button when it lays out its subviews.
This is what you have to do to change the title text for a button’s state.
[calibrationButton setTitle:@"Calibration" forState:UIControlStateNormal];