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Probably the different between "we'll get a warrant" and "we have a warrant".
.https://www.uswitch.com/gas-electricity/guides/energy-back-billing/amp/
Is looks like this may help. Unless it was a valid bill that you've received and just not paid.
If you don't have a smart meter, going forwards, set a reminder on your phone, to take and submit meter readings each month. Or a week before your next billing date. Saves getting the wild estimate bills.
So they just lied about it? Seems likely.