Angular 5 Update Parent Component value from child Component

You have not marked OpenScheduleCall as an input to the child component, so first of all you need to do that. And to achieve two-way-binding with banana in the box, your @Output needs to be the @Input variable name, with the suffix Change. So first mark the variable OpenScheduleCall as @Input to child and then change the name for @Output variable:

export class ChildComponent implements OnInit {

  @Input() OpenScheduleCall;
  @Output() OpenScheduleCallChange = new EventEmitter<boolean>();

  onLog() {
   this.OpenScheduleCallChange.emit(false);
  }
}

Now you have two-way-binding:

[(OpenScheduleCall)]="OpenScheduleCall"

Just Output cannot be in two-way data binding. Add also () at the end of the bounded function.

(OpenScheduleCall)="YourFunctionInParent($event)"