I have recently left VM as I needed to move out of the UK. My contract expired on the 31st of December 2019 and the last payment was due on the 19th. At first I have received an email saying I was due a payment for the next bill on the 20th of January 2020 and this is what my billing page looked like:
If you have cancelled your account fully then this will be returned to you via a Cheque refund. The cheque will be processed around 35 days after your account closed and then we advise to allow 10 days for delivery.
If you just changed your package and are still with us with an active account, the refund will stay on your account.