Hey, check this out, this former corporate shill is going to tell you exactly how to even the score with this retail pond scum in the proper and effective manner. Credentials: For a long time, I've been knocking down those in positions of power who think they can use their position to press their thumb down upon those without power without fear of consequence. I absolutely love to show them the folly of that particular belief. This is nothing; I was taught this particular method by an old mentor.
1) Find out who owns the store. Google might tell you, or you could go in, ask to speak to a manager, and ask him/her for the owner's name and address. They'll want to know why - do not under any circumstances tell them, or they'll get out ahead of you and this plan will fail.
2) Now that you have the owners name and address, it's time to write a letter (more about that below). Hand-write the letter and hand-write the address on a standard envelope (black pen) - make it a point to use your best penmanship, no cursive. Do not email, don't call unless the owner responds and invites you to, and I'll tell you why: emails can be easily ignored, you'll never get through if you call, and taking your complaint directly to an in-store manager will result in your complaint getting "lost in the mix", usually accidentally on purpose. If the people are how you describe, it's a corrupt culture from the salespeople up to the head manager. Owners are usually unaware this is going on, and they're usually in favor of cutting out such a cancer when they're made aware of it.
3) There are a number of key elements to include in this letter (and not necessarily in this order), but yes it all matters, and an explanation as to why will follow:
-A formal, business-type greeting; no "Dear Mr. XYZ" - too familiar. Try something more like "Greetings and salutations, Mr. XYZ".
-The date and approximate time you were there. This will allow the owner to check who was working at the time, since I'm betting you didn't take down the perpetrators' names.
-If you did happen to catch some names, include those. If not, no big deal, see above.
-A detailed account of everything that happened in sequential order, from the moment you walked in the store to the moment you walked out. When you describe the offenses against you, include how it made you feel and especially how it impacted your shopping experience.
-At the end, you need a subtle but powerful closer. I would recommend something like "I doubt I shall ever revisit your establishment if this is the type of treatment I can expect from your employees." In fact, use that. Definitely not anything in the vein of "I'll never come back period", and definitely not nothing. Just something in the middle that will subtly spur the owner to action.
-Common mistake, so it's worth it to mention, end the letter with "Sincerely,"; it's easy to make a mistake and put "Love,". That just comes off as weird. You want to appear to be a perfectly normal, well-adjusted person in this letter to reduce the chance of victim-blaming and summary dismissal.
-Include your full name and contact info (phone, address, and email) either in the bottom-left or the header.
Now, as to the "why?" with all this? The letter has to go to the owner because usually when employees are corrupt, management is corrupt too. It has to be a hand-written letter because while the owner can ignore all other forms of communication, he will open his mail, and *boom* - there's your complaint right before his eyes. Hand-written because it reminds the reader that a real person wrote this - it's as familiar as you can get without crossing the boundaries. The general rule is that hand-written letters get responses, emails and form letters get ignored. This is true from small businesses all the way up to Google and Apple. Black ink because colored inks are unprofessional.
Also, I really, truly hate to say this, but it's really important: do NOT at any point in any way at any time mention you have autism. We don't currently have the minority status that would make for an easy-win lawsuit, which would be the only reason that would make it worth it to disclose. In reality, nobody cares that we have autism, the more likely response is for them to think you're making excuses for yourself or crying for special attention or trying to manipulate them using your disability as leverage. Simply put, the risk vs. reward ratio for disclosing is absolutely terrible; plus, disclosing gives people full, socially-acceptable permission to put you in a box, view you as inferior, put the blame on you, and dismiss your concerns. It's ****ed up, but hopefully that changes some day.
The end result will be: worst case scenario, those employees get some sort of disciplinary action. Best case scenario, the owner guts the entire work force. This whole thing sounds really specific and kind of off-the-wall, but trust me, I know what I'm talking about and it works.
Use it or don't, but either way, good luck