I have to fire an observer method when the admin assign customer(s) to group on adminhtml. Can you help me which event is it?

I tried adminhtml_customer_save_after but it didn't worked.

I have to fire an observer method when the admin assign customer(s) to group on adminhtml. Can you help me which event is it?

I tried adminhtml_customer_save_after but it didn't worked.

Edit: My config.xml

    <adminhtml>
        <events>
            <adminhtml_customer_save_after>
                <observers>
                    <vendorname_packagename_customerconfigobserve>
                        <type>singleton</type>
                        <class>Vendor_Package_Model_Observer</class>
                        <method>observeCustomerConfig</method>
                    </vendorname_packagename_customerconfigobserve>
                </observers>
            </adminhtml_customer_save_after>
        </events>
    </adminhtml>