If we are going to be charged for data overages then you should offer an ability to limit data usage WITHOUT having to pay for that too! We need to switch providers. This is ridiculous!
Most limited data plans have safety mode which is free, you just need to make sure it is on.
What plan do you have?
you can also set alerts for x% of data left.
not be charged for data if you go over, maybe your bank wouldn't mind if you write checks for money you don't have in your account.