I want caller to leave a message if I do not answer for any reason. How can I do that in my Nokia S30 or S40 phone?

Activate Call divert (or Call forward) to your voice mailbox so that the caller can leave message there if you do not answer.

To activate the feature, select MenuSettingsCall settingsCall divert (or Call forwarding) and the situation under which a call is diverted, and then enter your voice mailbox number provided by the service provider or select a number from the phonebook.

Note. This feature is a network service, if not available, contact your network operator or service provider.