A question about notifications

I was lucky enough to get the AT&T unlimited data plan for my ipad but my husband just got his pad and signed up for the 250mb plan. I thought there was some way for a person to be notified by AT&T when they are getting close to their limit but I cannot find it in the settings. Anyone know where this might be??? Thank you.

 

It happens automaticaly, you cant turn it on or off.

if you go into settings and usage it will also show how much data has been used.