Earlier quoted context omitted.
The appeal process is filing a lawsuit against Slack, provided the person wronged didn’t already agree to give up that right when accepting Slack’s TOS.
Even if it wasn't given up, what would the lawsuit complain be, and what would one gain from it if it succeeds? Isn't Slack legally entitled to shut down any accounts at any time?
Two, they may have to at least return the data: if I let you use a desk at my place and you start doing business there, I am pretty sure I cannot legally refuse you entry and hold on to your papers.
Three, even if they are, we're also legally entitled to call Slack incompetent losers, and to tell our employers that we should not switch to Slack if we wish to continue being co-workers with Iranians. I will be telling my employer that shortly. (One fascinating aide effect of using Slack is thst the entire company must conform to Slack's policies. You cannot hire someone whom Slack won't create an account for, nor someone who won't agree to Slack's ToS, because if they're not on Slack they can't get work done.)