That is weird:

I'd write back on 14 November 2024 as follows:
Dear North Essex Parking Partnership,
Many thanks for your letter of 24 June 2024. I never made any payment in respect of this PCN, but I note the amount outstanding is zero and I therefore take it that you have cancelled the penalty.
Article 16 of GDPR states that:
"The data subject shall have the right to obtain from the controller without undue delay the rectification of inaccurate personal data concerning him or her. Taking into account the purposes of the processing, the data subject shall have the right to have incomplete personal data completed, including by means of providing a supplementary statement."
I require you to amend your records to show that the penalty was not paid, and was instead cancelled by the council.
If you do not accept that the penalty was cancelled and you are convinced that the penalty was paid, please treat this as a subject access request for any records you hold confirming that I paid the penalty.
Yours faithfully