What happens to the ball's velocity while the ball is traveling upwards?

If the ball does not have a propeller or jet engine on it, then it is an object
in free fall.  That means its downward speed grows by 9.8 m/s for every
second that it's in the air. 

If it happens to be traveling upward at the moment, then that won't last long. 
Its upward speed is decreasing by 9.8 m/s every second.  It will eventually
run out of upward gas and start moving downward.  At that instant, you might
say that the direction of its velocity has changed by 180 degrees.