How to update a specific row from pivot table in laravel 5.6?

I have this model in Organization.php

public function agency()
{
    return $this->belongsToMany('App\Agency')->withPivot('status');
}

and this model in Agency.php

public function organizations()
{
    return $this->belongsToMany('App\Organization')->withPivot('status');
}

How can I update the status of a specific row in my pivot table? This is my code in the controller:

public function removeAgency(Request $request){
    $my_agencies = Organization::find($request['org_id']);
    $member = $my_agencies->agency()
        ->where('agency_organization.agency_id', $request['agency_id'])
            ->first();
    $member->pivot->status = 'removed';
    $member->pivot->save();
}

It returns an error saying: "Creating default object from empty value"

via Chebli Mohamed