You can reach us in several ways:
By mail
De Nederlandsche Bank NV
Expert Centre on Market Access
PO Box 98
1000 AB Amsterdam
Telephone
DNB Information Desk, open on business days between 9:00 am and 5:00 pm (0800 020 10 68 in the Netherlands, or +31 20 524 91 11 if calling from abroad). 
E-mail
info@dnb.nl (please state your name, address and telephone number)
We will not consider anonymous questions.