Method update does not exist in Laravel

It is very simple code to update an existing entry. save() is working perfectly. But update is not working. Here is my code:

Route::post('toggleFavourite',function(){
    try{
        $data = Request::all();
        extract($data);
        $favourite = \ItScholarBd\Api\Models\Favourite::where(['user_id'=> $user_id,'shop_id'=> $shop_id])->get();
        if(empty($favourite)){
            $favourite = new \ItScholarBd\Api\Models\Favourite;
            $favourite->user_id = $user_id;
            $favourite->shop_id = $shop_id;
            $favourite->status  = $status;
            $favourite->save();
        }else{
            $favourite->status  = $status;
            $favourite->update();
        }
        return response()->json(['status' =>1, 'data' => $favourite], 200); 
    }
    catch (Exception $ex) {
        return response()->json(['status'=>0, 'status_text' => $ex->getMessage()], 500);

    }
});

I am getting the following response:

{"status":0,"status_text":"Method update does not exist."}

via Chebli Mohamed