In August I returned a car hired through Europcar and subsequently found I had been charged €77.75. It explained the sum was for refuelling the vehicle and some damage which it could not specify. I had photographed the petrol gauge on returning it since I’ve had trouble with wrongly levied fuel charges before. Also, there was definitely no damage. I complained to Europcar and was repeatedly promised a response, which has never come. PF, London

• We hired a car from Europcar in Italy in June and received a statement of account a couple of weeks after returning it advising that there was nothing owing.

Subsequently I discovered that Europcar had debited €92 from my card. I had no idea why and after numerous calls and emails to which I received no response, I was told I must have committed two traffic violations and Europcar had therefore charged me €45 for each of these. I pointed out that two fines of €45 only makes €90 but could not get to the bottom of this difference.

I have no idea whether or not I did commit the alleged traffic violations, since I’ve heard nothing from the Italian authorities, and am concerned that Europcar appears able to just debit my account without even notifiying me three months after I have rented the car. CE, London

• I rented a car from Avis/Budget in London. We returned the car on a Sunday night and as there was no attendant, I called the next day to make sure that everything was OK.

I was told that there was a small dent in the rear bumper and a broken reflector. I asked him how much the repair would cost, and he told me that his systems were down but that he’d call me the next day to let me know.

However, that night, there was a charge of £520 on my credit card from Avis/Budget. That seems rather steep for a small dent in a plastic bumper. I called to inquire about the claim, and was told that it wasn’t filed. Ditto the following day. This time the customer service agent told me that complaints/inquiries were only considered by email. So, I emailed a formal inquiry asking them to provide me with a claim, a copy of their repair pricing policies, and a repair estimate (that justifies the extent and the cost of the repairs). No one has ever got back to me. MM, London

These are not the first cases of car rental companies helping themselves to little extras without warning or explanation, usually when vehicles are returned out of hours and culpability for any damage can’t be thrashed out on the spot.

In PF’s case, Europcar insists that the tank was not full and that there were scratches on the bumper. You dispute this. However, because of the months it has taken the company to respond to your complaint it has decided to refund you.

You, CE, should have been informed of the charge to your card by letter, according to Europcar’s protocols. However, under Italian law the company says it is obliged to pass on a hirer’s address to the police in the event of a traffic offence, but is not privy to the details of the contravention.

Europcar awards itself a generous €48 per offence for the paperwork required by the relevant authorities (despite failing to send any paperwork to you).

As this column has exposed before, Italian law allows authorities up to 360 days to issue fines to foreign drivers who contravene parking regulations, so it could be a long while yet before you discover what you’re supposed to have done wrong.

Now over to Avis, which apologises for the fact that you, MM, were not contacted about the repair costs, but stands by its large charge for the damage since you did not take out additional insurance.

The terms and conditions of the rental agreement, like most other hire companies, specify that extra charges will be removed from customers’ accounts in the event of damage. If you are returning a car out of hours when no one is around it is a good idea to photograph the vehicle in detail in case such disputes arise, otherwise it’s a question of your word against theirs. And they are the ones with your bank details.

If you need help email Anna Tims at your.problems@observer.co.uk or write to Your Problems, The Observer, Kings Place, 90 York Way, London N1 9GU. Include an address and phone number.