Alerts can be setup to send SMS messages. The default provider is the Telematics Guru provider. Partners will be charged for these SMSes. 

Partners can set a limit to the number of messages an organisation can send in the Organisation Setup (Admin->Organisations->Edit).

How do I know how many SMS messages have been sent by Telematics Guru in a month?

To monitor how many messages have been sent, the Sms Usage Report can be used.

Go to Reports->All Reports->Sms Usage Report.

This is an admin report, and may not be enabled for your user and/or organisation. Contact support to enable it.

The report setup is shown below. You may not see the filters if you belong to one Distributor and one Partner.

Note that Test SMS's, sent from the Adress Book interface, bypass the message counters, so they will not appear in the report.