… or anything along those lines, especially via text/email (or anything else that an employer could provide his proof during legal proceedings).
I see there’s a ton on this subreddit and I definitely see the appeal, but its a short lived victory the previous employer will enjoy more. If it helps you to swallow your pride consider it similar to giving your previous employer a “handy” (or cunnilingus/fellatio) your way out, because that's exactly what you're doing.
I get this might be really tempting if you have a second job or you just want to stick it to the man (which you can still do via creative name calling – Just don’t admit to wrongdoing or quit). If you say something along the lines of “I quit!” it can disqualify you from benefits that the employer would pay out (e.g. severance packages, unredeemed PTO, unemployment, etc.).
You might even be able to get the POS manager fired assuming they aren’t the owner. If they were the owner you could’ve filed a wrongful termination lawsuit to teach them a valuable lesson on how to not be a dickhead with future employees.
TL;DR – Don’t make your previous employees day by telling them that you “quit”. Hit them in their pocketbook, because that is what they care about.
Edit: While you're at it leave bad reviews on Glassdoor, Yelp, & wherever else you can. People look at this. I have turned down jobs based on their glassdoor reviews.