Replacement for Smart Limits Data Limits functionality

The fact that AT&T killed off the Data Limits function in Smart Limits before the promised replacement service was ready is frustrating.

The fact that AT&T have been totally silent on the date and features of this replacement service is unbelievable.

I used to use the Data Limits feature to block my kids from data. I set the limit to zero MB, which meant no data but picture messaging still worked.

When Data Limits retired, data continued to be blocked but now picture messaging doesn't work either (sending or receiving).

I can't go in to Smart Limits and remove the Data Limit to reenable picture messaging as that feature is no long accessible on the Smart Limits web page, plus this would turn all their data on (which I don't want).

I can't turn data on for each line in the main Account web page as it already says it is on (and challenge of not wanting all data access still applies).

How can I block general data access for my kids but still allow their picture messaging to function?