* To temporarily cancel cruise control: Press the brake pedal or the clutch pedal (if it's a manual transmission). The cruise control will immediately disengage.
* To turn off cruise control completely: You typically need to press the "CANCEL" button (often marked with a square or a cross) on the steering wheel. The exact location of this button will vary slightly depending on the trim level, but it's usually part of the cruise control stalk.
If your cruise control isn't working after trying these, there might be a problem with the system itself (a fuse, a faulty switch, etc.). Consult your owner's manual for troubleshooting steps or take it to a mechanic.