4gb shock free data and my daughter still goes over. How can I block her from using extra data
A way to restrict the ability to say yes to the main account holder line is being looked into, but until then, you'll have to look for ways to recoup the money if say you provide some sort of allowance, or shift her onto prepaid and make her pay for data use out of her own pocket sort of thing if she won't listen and just keep[s going over and replying yes each time.
You could put a data block after a pre determined limit in the smart phone itself or shut the data off for certain apps if she's not that tech savy and doesn't know how to undo those actions. It should be under cellular then data usage, just look for the data option and then set the limits.