Reclamo N° 244491

Hi, I am sorry to contact you but here is my problem (I am French I don't speak Italian...): I rented a car at Sixt Italia (Firenze statione) in August, and I just got an email (3 weeks after I braught back the car) that the engine was broken. They think I had an accident and broke it. But I did not have any accident. Actually I think the engine was already broken because the car had almost no power, shifting gears was a long process (it took many seconds to accelerate which was dangerous when I was on a highway). So I think the rent me a dangerous car and now they want me to pay... (I swear I was careful, I had no accident, there was no strange noise). So I am very concerned about that because , even if they did not provid an invoice, I am sure it gonna cost a lot). Do you have advices for me ? Thank you very much