They could have arranged with Telstra to cut off service to any meter that billed over $X in a month.
In fact, that should have been an obvious step to make, because a meter that was sending too much data was probably buggy, which could mean the data it was sending was probably worthless. The engineers who failed to include the cutoff were insufficiently paranoid.
What about meter diagnostics? "Cut off" means "cut off"; what if the utility needs the capability of remote snapshotting the memory or current firmware rev of a meter? (Having done multiple smart meter security review projects: this is not a crazy notion).
Yes, fellow geek, there will be some number that represents the maximum amount of bandwidth that might ever be used to diagnose a faulty meter. How much would it cost to figure that out? Again: weigh that against the business benefit of doing so.
The person who abused the meter SIM did not accidentally do so.
They could have arranged with Telstra to cut off service to any meter that billed over $X in a month.
In fact, that should have been an obvious step to make, because a meter that was sending too much data was probably buggy, which could mean the data it was sending was probably worthless. The engineers who failed to include the cutoff were insufficiently paranoid.