The API Text report page appears in the left-hand column of the REPORTS page if you have purchased the service to send text/SMS messages to specific phone numbers, inside or outside the network.
To get there, click on Reports - API Text:
The start of the message body appears as the title of the message. The first screen tells you how many messages were sent and if any failed. Click on the title to view details for each message:
Here you can see the number the message was sent to, the time and date it was sent, and which numbers were successfully reached. From the upper right-hand corner, you can also export a CSV file with the detailed report.