private function buildPhoneNumber( PhoneNumberType $phoneNumber , AbstractPayPalMessageFactory $factory ) {
		$phoneElement = $factory->createMessageElement();
		$phoneElement->addChild( $factory->createMessageField( 'countryCode' , $phoneNumber->getCountryCode() ) );
		$phoneElement->addChild( $factory->createMessageField( 'phoneNumber' , $phoneNumber->getPhoneNumber() ) );

		if ( ( $phoneExtension = $phoneNumber->getExtension() ) != null ) {
			$phoneElement->addChild( $factory->createMessageField( 'extension' , $phoneExtension ) );
		}

		return $phoneElement;
	}