Open Report Wizard and run the absent report for all students for the day in question. Find the student on the list, right click their name and select Get Call Attempts. This will show you all of the calls made to the contact numbers you have for that student. You may notice some say Answer Machine Message Left under the description column. The call the parent is receiving will be from their answer machine reminding them that they have an answer machine message. Truancy Call will not send any calls if there has been a response or the school have stopped the call.
The only time a parent will carry on receiving calls is if they call the school directly (rather than answering the call from Truancy Call) and the person they speak to does not update Truancy Call and stop the call.