Charged Late Fee. How do i dispute this?

[AwfulService1]

Original credit purchase was Nov 6th '21, and was £369.99

Minimum payment was £30, but I paid £100 on Dec 3rd '21.

Saw a message (Paypal App) before Jan 1st '22 that said I could ignore minimum payment if I already covered that payment.

Yet i've just been charged a lateness fee of £12. Despite paying enough to cover 3.3 months' minimum payment.

How can I dispute this?