Hertz Rental, I rented a bike for 5 days in Madrid. I paid for unlimited milage., When I arrived they said I had not paid for unlimited mileage. As I did not have All my paperwork with me, I could not verify this. On my return I complained. I did not get any help at all locally or national as they wanted a K or L reference number and my reservation had neither Make sure you take all paperwork with you when dealing with the bump price vendors (like rental and budget airlines) Otherwise you are easy prey.
If you paid by CC probably by Debit card too, and you can show an agreement giving unlimited mileage to the card provider, I expect they will refund you the over charge.
Sorry to read that. I guess the morale of the story would be to prepay, therefore locking the supplier into a fixed contract agreement?