// COLLECTION NAMES:
- user_1_list_1
- user_1_list_2
- user_1_list_3
...
- user_1_list_55

{
   first_name
   last_name
   phone
}

$collection_name = "user_1_list_1";
$collection = $this->db->{$collection_name};

$query = [];

$cursor = $collection->find(
    $query,
    [
        'limit' => 10,
        'skip'  => 0,
        'sort'  => ['first_name' => 1],
    ]
);