Payment due a 2 months after leaving?

I left Bulb in September, although in credit by more than a month, Bulb took another payment because I was too close to the payment for it to be stopped, which is reasonable .

Bulb requested I leave my direct debit open to make it easier to take any monies due and to refund the credit to be refunded, which, again, is reasonable.

In October, the day after my usual payment would be taken, bulb finalised my account refunded my credit and closed my direct debit. Great, thank you very much.

Today, I received a missed payment email for October for £11 stating that it is due by November 12th surely a mistake has been made.