Billed after switching to another ISP

[#1]

The switch date to the other supplier was 25/05/18 but I've just now been billed by Plusnet (31/05/18 ).  I've looked into my Plusnet account and it appears the service hasn't been cancelled despite receiving an email from Plusnet confirming the switch and internet access being unavailable on the day of the switch.  Any help in sorting this out would be much appreciated.

[#2]

Sorry to hear that.

Once this bill has processed we'll refund the money back and arrange for the account to be cancelled