From now on .AT ownerchanges are performed using the command TradeDomain:
command = TradeDomain
domain = <domain name>
ownercontact0 = <new owner contact handle>
Alternatively, you may of course use the respective function in the web interface (Domains > TradeDomain).
Additionally, you have to generate an ownerchange form at http://domainform.net or in the web interface at "Domains > Domain tools > .AT ownerchange". The form has to be filled out and signed, and then you have to send it to the number stated on the fax.
Please notice that you first have to execute the Trade command before being able to generate the fax.