..which is what I was trying to get at with the OP in my last post.
OP, you neither phoned the number nor did you pay sufficient attention while you were processing your request. It happens.
I suggest you change your approach to try and head-off their counter-arguments.
Perhaps:
I saw the sign and not unreasonably read Pay by phone as PaybyPhone, a common parking service provider to London councils. I did not phone the number, because this has a cost, instead I logged into my PaybyPhone app which processed my payment accordingly. It now turns out that the location number 6019 is not unique among service providers or to this location but instead exists with at least two in London, one at the location and the other in Barnet. Mistakenly, I paid to park in Barnet.
After I found the PCN I saw the APCOA and RingGo stickers on the post. I don't know whether their purpose is to inform motorists but frankly after the well-publicised problems experienced by Westminster Council with 'scam' QR codes on ticket machines I would disregard any information given in such a manner and instead rely solely upon the information embedded in the traffic sign.
Somewhat longer but as far as I can see brings into play every reason why they might say 'no' and is intended to give them cause to say yes, even if on a discretionary basis.