Got the following message and not sure why since it is a unlimited data plan. What did I do/what does this really mean and how can I prevent this from happening again? Thanks in advance! Oh, and I checked the usage on the phone and it said 5.05GB of mobile data.

Mobile data is now off

You've reached your specified data usage limit, so mobile data has been turned off.

If you turn mobile data back on, you may be charged for data usage by your carrier.

TURN ON DATA        OK