From HEXONET Wiki
It is not possible to change the owner name or company name of a .AT, .BE, .CH, .EU, .ES, .FR, .IT, .JP, .LI, .LU, .NL, .NU, .SE or .SG domain through the ModifyDomain command. In such a case you have to request a so-called "trade" and state the new owner contact. Please have a look at the Domain API-Manual for a current list of allowed parameters.
(required) command = TradeDomain domain = (DOMAIN) ownercontact0 = (CONTACT) action = request | cancel
code = (CODE) description = (DESCRIPTION)