You can book a cab via following methods:
Online: http://oncabs.com/booking/washington-dc
Telephone: +12026013768
Email: info@oncabs.com
Yes, it's possible to pre-book a cab with Oncabs Washington Dc, please contact the company.
Oncabs Washington Dc has both regular and air-conditioned cabs, please mention your preference at the time of booking.
Please contact the company on their helpline number to make any changes.
Generally drivers will meet the passengers at the arrivals on airport pick ups but do check with the company.