“How to get a refund…”
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Offgem have sent out the following public message announcement:
Are you owed credit on your energy bill? Learn how account balances work, why it might be a good idea to build up credit and how to get a refund if you think your current or previous supplier owes you money
Are you owed money on your energy bill? | Ofgem
With more useful information given here:
Your energy bill explained | Ofgem
And from other service providers too:
Claim back credit from your energy supplier – Citizens Advice
Does your energy company owe you £100s? – Which? News
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