Ive had regular car hire throughout europe for over 45 years and NEVER had this trouble before. We pre.ordered and rented two cars from sixt at hotel luna Albufeira. Everything was fine until the final invoice arrived 3 days after my return to the UK. One car invoice was fine, yhe second car invoice had a charge for almost €100 for fuel, despite us filling up the car and showing the full tank to Bruno, the advisor, almost 3 weeks later and 8 emails to both sixt portugal customer services (no replies whatsoever) and hotel luna desk, (1 reply, thanking me for the email) I have had no further replies or even acknowledgement of the problem. I am now having to contact my credit card company for some redress. Decent cars good initial service, but wait for the final invoice and start to fume... Avoid like the plague.