It's not clear from the attached documents whether your reps and their reply is for the PCN or the subsequent Notice to Owner. Are you the owner with your name and address on the V5C Registration Certificate for the vehicle ?
It would be best if you re-posted the documents in full, with headings and signatures.
If you are the owner, then you must wait for the Notice to Owner, and present your representations again. I see that they state they have cancelled a PCN before under similar circumstances, so are obviously not minded to cancel again.