I have had similar with Avdata at Rottnest. I land there several times a month and pay my dues however one time they charged a fee (in this case it is an Island Entry Fee) for a missed approach. After much to-ing and fro-ing and the Rottnest Island Authority insisting that a missed approach counted as "using the island facilities" (where we got into an interesting discussion about who owns the air) I just told Avdata I would sign a stat dec to say I didn't land there that day, that shut them up.
They have to prove you did land there, you don't have to prove you didn't.
There are people out there who think it is clever to use other people's callsigns on the radio.
It's just dishonest.
On the subject of landing fees, Airservices often charge twice for a TNC. if you land outside of half an hour of when the computer estimates you should from your flight plan, you get charged twice. So always check the bills carefully, they try to cheat me out of a few hundred bucks every year.