Help i have a similar situation with sixt in 2023

i hired a car. Videoed it on drop off and they tried to charge me for damage i did not do.

after three months this "false danage" was waived as a gesture of "good will"

i asked to be compensated for the stress and they ignored me so my credit card charged the rental back to my card.

sixt has now passed the debt to Pro factura who are threatening legal action if i do not pay.

what should i do now? Ammount is 750 euros.


please please advise and help