Test a mobile-data rollback with one reversible setting, one small data transfer, and a written before-and-after record. The goal is not to make the device use as much data as possible. It is to prove that you can return the phone to its prior policy after a change and still explain what the usage counters mean.
Capture a baseline that can survive the test
Start near the beginning of a billing period if practical. Record the carrier's current total and the phone's current total, along with the billing-cycle dates, active SIM or eSIM, and whether roaming is enabled. On iPhone, the cellular settings can show per-app usage, system-service usage, Wi-Fi Assist, and statistics that can be reset. On Pixel, the settings can show total and per-app data use and can expose warnings, limits, roaming, and background-data controls. Both vendors caution in different ways that the phone's measurement may not be identical to the carrier's record, so treat the carrier total as the billing reference and the device total as a diagnostic view.
Take screenshots or write down the numbers before touching any counter. If you reset statistics as part of the test, that reset itself cannot be rolled back; preserve the old reading first.
Change one control and run a tiny test
Choose a low-risk control: disable mobile data for one nonessential app, lower a warning threshold, turn off background data for a test app, or change Wi-Fi Assist only if you understand its effect. Avoid testing roaming while traveling, and do not create a billable overage merely to see whether a limit works.
With Wi-Fi off and a good cellular signal, perform one small, repeatable action such as loading a short text page. Record the start and end times and the change shown for that app. Confirm that the selected control behaves as expected. If the test app was blocked from mobile data, it should wait for Wi-Fi or fail clearly rather than silently falling back through another route.
Roll back and prove the old policy returned
Restore the exact original value, not a value that merely seems reasonable. Reconnect to the original SIM, warning threshold, app permission, background-data setting, roaming choice, and Wi-Fi Assist setting as applicable. Repeat the same small action and verify that behavior matches the baseline policy. Then check both the device view and the carrier view after their normal reporting delay.
The rollback passes when the original settings are documented, the test changed only one control, the original control is restored, and a second small action behaves as expected. It fails if you cannot tell which SIM carried the traffic, the billing cycle is wrong, or a usage counter was reset without first recording it.
Keep a compact rollback record
Save the date, device, operating-system version, carrier, line label, original value, test value, restored value, and evidence from the two test actions. Do not store account passwords, full SIM identifiers, or one-time codes in the record. Review the plan after an operating-system update or carrier change because menus and reporting behavior can change.
Sources
- Use cellular data on your iPhone or iPad — Apple Support
- Reduce and manage mobile data usage — Google