The ModifyContact command allows you to modify the WHOIS contact data of the domain:

COMMAND

 (required)
 command = ModifyContact
 contact = (CONTACT)

 (optional)
 title        = (TEXT)
 firstname    = (TEXT)
 middlename   = (TEXT)
 lastname     = (TEXT)
 organization = (TEXT)
 street       = (TEXT)
 city         = (TEXT)
 state        = (TEXT)
 zip          = (TEXT)
 country      = (COUNTRY)
 phone        = (PHONE)
 fax          = (PHONE)
 email        = (EMAIL)
 vatid = (TEXT)

 x-at-disclose = 0 | 1
 x-at-disclose-voice = 0 | 1
 x-at-disclose-fax = 0 | 1
 x-at-disclose-email = 0 | 1

 x-pl-consentforpublishing = 0 | 1

 delete0        = TITLE | FIRSTNAME | MIDDLENAME | LASTNAME | ORGANIZATION | STREET | ZIP | CITY | STATE | COUNTRY | PHONE | FAX | EMAIL | VATID | x-...
 delete1        = ...
 delete2        = ...
 . . .

IMPORTANT: Please have a look at the Domain API-Manual for a list of allowed parameters.

RESPONSE

(required)
code        = (CODE)
description = (DESCRIPTION)