What "fine"? I will give you £100 for every occurrence of that word you can evidence on any of the correspondence relating to this, including the pervious one where you appear to have been suckered into paying it!
Maybe you are referring to a Parking Charge Notice (PCN) which is definitely NOT a "fine". It is simply a speculative invoice from an unregulated private parking firm for an alleged breach of contract by the driver.
Would you just pay any old invoice just because it says you have to pay? This whole system is designed to get the low-hanging fruit on the gullible tree to pay up out of ignorance and fear. Sadly, that is the majority of recipients of these PCNs.
Regarding your specific case, you have provided little information that we can use to assist. Please read this:
READ THIS FIRST - Private Parking Charges Forum guideWE need to know the name of the operator. The location. Whether the PCN was issued as a windscreen Notice to Driver (NtD) or a Postal Notice to Keeper (NtK). Has the driver been identified? Is the PCN fully compliant with PoFA 2012?
Maybe just show us the PCN?