The other day we received the BPC monthly bill. The amount seemed a bit high, so I looked more carefully and discovered an "outstanding payment" for last month plus a penalty. Luckily, I remembered that I did pay last month's bill and even had the receipt. Going to BPC I learned that the error is not just in our bill, but in many people's bills. Apparently BPC moved to a new IT system which caused some glitches.
So: check this month's bill carefully. If you can't find last month's receipt (and you did pay!), you'll have to ask BPC's IT division to pull it from their system.
By the way - I tried to look up BPC's website for a notice (their website is extremely slow to load) but found nothing.