If I transferred from ATD 2020 to ATD 2021 and cannot attend, how do I change my registration? Natasha Porter Updated February 08, 2021 22:27 Follow Please contact ATD Customer Care for assistance. Email email@example.com or call +1 703.683.8100/800.628.2783. Please see the ATD 2021 cancellation policy. Related articles How can I sponsor your conference?