Ok, you need to write and make a formal complaint.
First Utility Customer First, PO Box 6363, Coventry CV3 9LR
They will investigate the matter and report back to you.
If they do not uphold the complaint then you can go to the Ombudsman.
They will offer a free, independent service and can not examine your complaint at:
That should resolve the matter for you.
Can I clarify anything for you about this today, please?
If not, I would appreciate a 5-star rating for my answer. If you need anything further I am available for a follow up at no extra cost.