On every occasion on which I’ve asked AVDATA to reverse charges that have been invoiced to my aircraft for flights to places to which I haven’t been as stated in the invoice, the charges have been reversed. Although I could have just not paid and instead sat back to wait for the debt to be proved - when it couldn’t be - AVDATA has always accepted my requests.
One problem with the ‘sit back and don’t pay’ approach arises if you get an invoice with charges for e.g. 6 aerodromes and you weren’t ever at e.g. 2 out of the 6. If you pay part of the invoice - because the charges are legitimately owed for 4 out of the 6 - but don’t say anything about why you’ve only payed $X(invoiced) - $(for the 2 aerodromes you’ve never been), AVDATA won’t necessarily know which charges you’re disputing. Again, although that’s theoretically not your problem, it’s easily resolved by a short email.
One interesting thing to watch out for: If you submit a flight plan to NIS for a flight that goes to a place that has a charge, you may still receive an invoice with a charge for that place even if you do not end up going there in fact. This seems to be programmed into NIS or a system that monitors NIS/Flightaware etc. Again, I just request a reversal of the charges in these cases, and the charges have always been reversed.
But on the day I request a reversal and it’s refused, my response will be: Go your hardest and prove the debt. I’m always looking for entertainment.