[ShurikEv]

Еще такой вот код работает

                // Create the SecurityPrincipal object.
                SecurityPrincipal assignee = new SecurityPrincipal();

                // Set the properties of the SecurityPrincipal object.'
                // PrincipalId is a GUID that identifies the user or team 
                // that will own this record.
                assignee.PrincipalId = new Guid("B05A92E4-E97B-DC11-8490-0003FF0C1ABB");

                // Create the target object for the request.
                TargetOwnedPhoneCall target = new TargetOwnedPhoneCall();

                // Set the properties of the target object'.
                // EntityId is a GUID that identifies the account 
                // that is being assigned to the user.
                target.EntityId = new Guid("807899CD-B582-DC11-B0C3-0003FF0C1ABB");

                // Create the request object.
                AssignRequest assign = new AssignRequest();

                // Set the properties of the request object.'
                assign.Assignee = assignee;
                assign.Target = target;

                // Execute the request.
                AssignResponse assignResponse = (AssignResponse)service.Execute(assign);