Your device uses the ETSI standard TS 127.005 to receive and request these SMS text messages, to store them and, if required, to log the receipt of an SMS to the SYSLOG. The entry in the SYSLOG counts as a "notice" to inform you about any important messages, such as a notification from an external instance, for example. An instance might be the accounting system of your provider:
If you connect to the Internet via a 3G/4G WWAN module and the contract with your Internet provider includes a volume limit, then depending on the contract your provider will throttle or stop data transfer once this volume limit has been reached. In countries with the appropriate legislation, this also applies when a charging limit for data roaming has been reached. Before the data transfer is throttled or stopped, many providers send an SMS text message informing the customer that the volume limit has been reached. With the corresponding notification settings in the SYSLOG and/or via e-mail, the device can immediately inform you about the reception of the SMS, so that you can respond promptly.
