There's a certain obligation on both sides of a contract to pay attention.
If you're not watching your billing, and then try to claim overcharging a year later, you'll get a lot less satisfaction even from regulators or judges than if you notice it when (or soon after) it happens.
No argument, but fuck-ups happen, and get fixed more quickly and easily when people are paying attention.
I once got a monthly water bill for ~$35,000 at a residential, single-family home. Good thing I was paying attention and looked at the bill before the auto-pay bank draft hit.
If you're not watching your billing, and then try to claim overcharging a year later, you'll get a lot less satisfaction even from regulators or judges than if you notice it when (or soon after) it happens.