Magento – how to get customer information using event observer

I got my solution describe flowing:

magento customer registration 2 way 1. Create Account directly from sinup form 2. Create account order checkout time

The Above module work only for customer_register_success observers events work when customer Create Account directly from sinup form.

When customer create account order checkout time we need to add flowing

Add following Line Top of success.phtml

    // Retrieve order
    //$_order = new Mage_Sales_Model_Order();
    //$orderId = Mage::getSingleton('checkout/session')->getLastRealOrderId();
    //$_order->loadByIncrementId($orderId);

    // Start Send Emai Here......
    $order = new Mage_Sales_Model_Order();
    $incrementId = Mage::getSingleton('checkout/session')->getLastRealOrderId(); 
    $order->loadByIncrementId($incrementId);

   //Start New Customer Registration SMS Here           
    $customerAddressId = Mage::getSingleton('customer/session')->getCustomer()->getDefaultBilling();
    $address = Mage::getModel('customer/address')->load($customerAddressId);
    $msisdn = $address->getTelephone();                     
    $quoteId = $order->getQuoteId();
    $quote = Mage::getModel('sales/quote')->load($quoteId);
    $method = $quote->getCheckoutMethod(true);
    $customer_email = $order->getCustomerEmail();
    if ($method == 'register'){ 
    //code to handle if customer just registered to your site
    //START SMS API Code here your code

    //ENd SMS API Code here your code

     } elseif($method == 'guest') {
    //code to handle if customer is guest
     } else {                
    //code to handle for logged in customer
     }  
   //END New Customer Registration SMS Here  

If you are getting message in log then your observer is being called. There is no issue there.
So, now the issue is related to get billing information of the customer. Try loading customer before you get customer billing address.

class Kbethos_CustomerGrouped_Model_Observer {
    public function customerRegisterSuccess(Varien_Event_Observer $observer) {
        $event = $observer->getEvent();
        $customer = $event->getCustomer();
        $customer = Mage::getModel('customer/customer')->load($customer->getId());
        $billingAddress = $customer->getPrimaryBillingAddress();
        if ($billingAddress) {
            $countryId = $billingAddress->getCountryId();
            switch ($countryId) {
                case 'US':
                    $customer->setData('group_id', 1);
                    $customer->save();
                    break;
                default:
                    $customer->setData('group_id', 27);
                    $customer->save();
            }
        }
    }
}

Or you can also use

$billingAddress = $customer->getDefaultBillingAddress();