It does not shutdown automatically unless there are No Connections. Unless of course, you’re using a Prepaid Jetpack and your data plan expires or runs out of data.
If you used all of your data on the first day then you can call Customer Service (800) 922-0204 to increase your data plan. Also, consider using a more proactive approach at managing your data allotment. A good idea is to divide the amount by (30) the number of days in the billing cycle and get in the habit of using no more than that on a daily basis.