ensure the child device is powered off prior to adding or removing limits.
From the Smart Family parent app, select the appropriate family member from the top row of contacts (multiple may appear).
From the Manage controls section, tap Limits.
Tap Text limit.
Enter the text limit.
Once the limit is reached, text messaging is restricted (except to/from trusted contacts) until the next billing cycle.
Your child receives a free text alert when they're within 15 messages of the limit; You receive an alert once they've reached the limit.