Talking Tech I-tiva is a third party, proprietary, product that libraries can subscribe to. Learn more here: http://www.talkingtech.com/solutions/library.
Be sure you've run installer/data/mysql/atomicupdate/Bug-4246-Talking-Tech-itiva-phone-notifications.pl to install the required data pack (new syspref, notice placeholders and messaging transport preferences)
To use, TalkingTechItivaPhoneNotification syspref must be turned on.
If you wish to process PREOVERDUE or RESERVES messages, you'll need the EnhancedMessagingPreferences system preference turned on, and patrons to have filled in a preference for receiving these notices by phone.
For OVERDUE messages, overdue notice triggers must be configured under Koha -> Tools -> Overdue Notice Triggers. Either branch-specific triggers or the default level triggers may be used (script will select whichever is appropriate).