Standing Charge overcharge by First Utility

uksal

I have an outstanding complaint with First Utility about being charged an additional day standing charge for Nov-Dec. It is the princely sum of 19p plus VAT.
My question is do any of you check your bills to make sure they are 100% correct? If every First Utility Customer was over charged for this period to the same value I estimate that they had a bumper Christmas Bonus of £190k (assuming they only have 1 million customers, which they claimed to have in 2014) and the VAT man would have gained a Bonus of £9,500.
The bill I have queried with them covered the period 29 November to 28 December. That's 2 days in November and 28 days of December totalling.......you've guessed it 31 days!!!!!!!!!
Jonathon on the phone said I was mistaken and that they charge for every day.......Georgia the supervisor didn't quite get it either and said it would take 8 weeks to resolve.
I'm still waiting for any response and have given them a nudge today to look at my complaint, but I'm intrigued, are they singling me out to take an additional 19p because they know I'll notice - or hope I won't, or do they really think that there are perhaps 31 days in November?, and everycustomer was overcharged.