How can I be sure the driver will show up

I will be needing a ride from Union Station Chicago, IL to Ohare Airport Terminal 1 on December 23. I won't have much time from the arrival of my train and the departure of my plane. I need a ride that is reliable.  How can I be sure my driver will be there? The last time  I traveled the driver canceled twice. I ended up getting a cab. I won't have the extra time to wait and then find a cab.