Вы можете попробовать это для получения данных текущего месяца:
$currentMonth = date('m');
$monthlysubscriptionupdate = DB::table("billings")
->select("billings.phone","billings.email","billings.plan","billings.created_at","users.username", "users.msisdn", "users.auto_subscription")
->join("users","users.username","=","billings.username")
->where(['users.package_id'=>'1102', 'users.auto_subscription'=>0])
->whereRaw('MONTH(billings.created_at) = ?',[$currentMonth])
->orderBy("billings.created_at", "desc")
->get();
Или, если вы хотите получить последние 30 дней, попробуйте это:
$date = \Carbon\Carbon::today()->subDays(30);
DB::table("billings")
->select("billings.phone","billings.email","billings.plan","billings.created_at","users.username", "users.msisdn", "users.auto_subscription")
->join("users","users.username","=","billings.username")
->where(['users.package_id'=>'1102', 'users.auto_subscription'=>0])
->where('billings.created_at', '>=',$date)
->orderBy("billings.created_at", "desc")
->get();