I'll be honest, we too have an account that gives us a month to pay ...
... I make the assumption that our cats & dog are included (they are working animals, ratters & guarder!)
... and sometimes, like now, I don't pay it within a month. As long as I go in & pay them something during the month, they wait for the rest. They did offer me an agreement last year, whereby I had to pay £10 every week... seeing as nothing happened when I missed by forgetting , I stopped worrying!