In order to make the registrant change, log into your domain reselling via your myhosttech customer center and switch to the expert mode.
Then go to Domains in the navigation menu and select Change Registrant. There you will find a button Start change of registrant in the upper right corner. Now you can enter the corresponding domain in an input field. If you want to perform the change of registrant (owner) for several domains, you can do it in one step. Add the domains in question one below the other in the input field.
Now you can either manually enter the new owner data or select an existing contact. To do this, open the drop-down menu at Contact ID and select the appropriate contact.
Alternatively, you can make the change via API in expert mode. To do this, go to Support > API, where you can enter the command in the input field. Here you can find the necessary command:
(required) command = TradeDomain domain = (DOMAIN) ownercontact0 = (CONTACT) action = request | cancel