Cancelled Service, paid final bill, so why did you just invoice me?

[#1]

Can't login to my account because you've deleted it. I moved house so had to cancel your service since you didn't offer fibre in the area I moved to. All got cancelled, though I also got stung with a £35 cancellation charge despite being out of contract. Something about the equipment you sent me for free that I've never even used. Anyway. Moving on from that little gripe I have just received an email that a further £4.02 will be taken for my service on the 18/09/14. But I do not have a service with you any more, there isn't anything to bill. I don't have an account, I am not a customer any more.
Account username: danielplatt
Direct Debit Reference: PNET1661362-1
If someone can let me know whats going on. Don't have phone line or anything installed in the new house so can't call.

[#2]

Hi danielplatt,
Really sorry for the confusion here.
Usually, a final invoice will be raised for any outstanding call charges and extra data usage fees after your account has closed. This is because they are charged in arrears.
There was £4.02 of calls made in August which were not inclusive of your plan at the time.
As you no longer have phone with us, this is the very last bill that we can ask of you.
Sorry again, and I wish you all the best with your new provider.
Thanks,
Matty

[#3]

Fantastic, had a suspicion it might have been calls but couldn't login to check so it was just like, well, what can it be and how long will it last.
Thanks for your help, that puts my mind at ease.

[#4]

A question - why is an account cancelled and portal access removed before the final bill (phone charges which are in arrears) is sent and the money requested and received from the direct debit
Surely a customer has the legal right to see the bill details as the email doesn't give that information

[#5]

@OJ - That is actually a really good question.
In the past, I have turned the portal access back on for people who needed access to phone calls that were made, and a breakdown of their bill. However this is a reactive practice.
I will look into raising this, but whilst we're waiting on the new billing system to come through, I'm not sure how much movement I'll get.
Thanks,

[#6]

BE were also a nightmare for cutting off access to their billing pages and forum as soon as you deactivated with them.
I had the usual "you owe us money but you can't get on to see why" situation when I left them.