Good afternoon. As we explained to you today, before you wrote your review:
The reason that you received an unexpected invoice, is because you did not send a cancellation request in writing, so the finance department were unaware of your wish to cancel.
The member of staff who you informed asked you to please inform the Office in writing (by email) so that your cancellation can be processed. As you did not do this, the news did not reach our finance department.
However, soon as you raised this with us today (that you have received an unexpected invoice, asking us why) we explained the above, voided your invoice and processed your cancellation, giving you confirmation of the same.