Like many people, I do a job that means dealing with the public. This, sadly, means sometimes dealing with people who are arseholes. Worse than that, not just people who are naturally unpleasant owing to genetic misfortune or a chronically unpleasant upbringing. Among the worst people are the ones who have chosen to be like this because they think it is better. Well it isn't better, you are the bane of the lives of numerous people, and it isn't even that advantageous to you. Stop it.
Abrasive is better for getting things done.
Well, no, it isn't. Let me paint you a picture. You've come in to my shop with what is in fact a reasonable and justified complaint. In order to make it clear who's boss, you decide to open by being cross and giving me a lecture about your rights. Small hint: if you are going to be a pompous windbag, get your facts right. I have been lied to many times by people demanding refunds and they often go for bluster. I've quickly decided you're probably one of those. Yes, I know I shouldn't be making those kind of snap judgements, but because of your opening monologue I'm on the defensive.
I'm not saying that from here you aren't getting your refund, but you haven't made things easy for yourself. If, for example you can't find your receipts then bad luck, I'm going to be precisely as helpful as the law dictates. You've likely made your bed with the rest of the staff too, because I told them all what a pain in the neck you were. I know we're supposed to be friendly and helpful and you're not under any sort of contractual obligation to be nice but unpleasantness makes people stressed and forgetful. Mistakes happen.
Ah but what about that total jerk who is also your boss? You respect him don't you?
I've met a worrying number of people who seem to think that being nasty is a legitimate management style. Part of the problem with this is that much as there is a sort of anecdotal connection between customers who are rude and wrong being an arse at work makes you look incapable. If you were good at your job people would respect you for that. You'd have no need to prance around being odious. Also, people are more likely to listen to you if you're good at your job, because you know what you're talking about. You could try being likeable. I know people who are terrible at what they do but carried by colleagues because they are well liked. Even if you're not terrible at what you do, we all need the support of our mates at some point. If you have neither respect or favour you will find that contempt is no sort of substitute.
Of course there is the dead scenario where you are neither successful or likeable or even right. You have nothing going for you here. Abandon your grievance or change your job. In either case the solution could be writing an ill-tempered blog.