I'd like the ability to set a dollar limit (hard stop, not just a warning) on data charges. This would apply to pay per use as an absolute limit and to data plans as an overage limit. This limit would be the total data charge whether it be from the home network or roaming. Ideally customers would manage this online through self serve and be able to adjust it as necessary.
This would help the following situations:
1) Kids prepaid phones where the parent wants to allocate a data quota in terms of dollars, like an allowance.
2) Many kids/seniors/casual users don't require data but need to unblock data for MMS texting. Set a $0 or very small limit so there are no unintended charges due to accidental usage.
3) Limit exposure to roaming data bill shock.
4) Have predictable phone bills in order to budget properly.