The Text Activity report can be found under the Reports (menu) > Find Reports > Email/Text/Marketing (left menu) > Text (tab) > Text Activity Report.
You can search texting activity by date range and who the text was sent to (Contacts, Students, Staff). This report will also provide a listing of who has opted out by replying 'Stop' within the specified date range.
Save this as a frequently used report! Click the heart (icon)next to a report name, the heart will change to redand the report will be listed under the Reports (menu) > My Reports for quick and easy access!