Weve just had a similar problem when leaving our service apartment. They sent a bill for 1100chf for cleaning the appartment after my wife and i spent two days cleaning it thouroughly. We refused to pay the bill and complained about the charge. After a few days they came back to us with an apology, that the apartement was cleaned satisfactory apart from one section in the Kitchen, which needed extra work. They reduced the bill to 300 chf. We were happy with that and paid up. Just shows it pays to complain, if yoru in the right and stick to your guns...