Hi @Mash
Thank you for your question.
It's unusual that the bill would still show due if you've made the payment.
It's quite possible that depending on the way it's paid as it can take up to 2 business days to process, that this is why it was still reflecting as due.
Coincidentally, I received my bill today, so I've gone and paid it early through the app, which has updated it to pending. I'll keep watch on it to see what happens, trying to replicate what you have seen.
Thanks, Chris