You should have told them your pronoun was "Fuck You". If they refused to use it you should have insisted and told them you were extremely offended at being referred to as Mr. , Mrs., or Ms. and would bring over their boss and complain and possibly consider legal action if they didn't continue the entire transaction with "Will that be all FuckYou *****?". etc...
“Hey, don’t worry; don’t be afraid, ever. Because this is just a ride…. And we can change it any time we want. It’s only a choice. No effort, no work, no job, no savings of money. Just a simple choice, right now, between FEAR and LOVE.” - Bill Hicks