whenPivotLoaded is not working . Always return blank

[afsalchemban]

This is my resource file

public function toArray($request)
    {   
        return [
            'id' => $this->id,
            'name' => $this->cname,
            'start' => $this->whenPivotLoaded('company_package', function () {
                return $this->pivot->start_date;
            }),
        ];
    }

Company Model

class Company extends Model
{
    //
    public function packages(){
        return $this->belongsToMany('App\Package')->withPivot('start_date');;
    }
}

Package Model

class Package extends Model
{
    public function companies(){
        return $this->belongsToMany('App\Company')->withPivot('start_date');;
    }
}

Controller
return new ReportResource(Company::with('packages')->get());

What I am doing wrong .Please help