Slack is an American company, GDPR is a EU law and OP is Iranian. That’s not how this works... Sure companies that operate within the EU have created tools to export your data automatically (they still have contact points to request the same data if you don’t have an account or were banned so can’t use the automated tools) so they opened those tools up to everyone not just those within the EU. But that doesn’t mean you are covered by the EU law and can demand your data. Only thing I would suggest is to lookup the GDPR email for slack and manually request the data. Though I wouldn’t expect anything.
US companies are forbidden from doing business with Iran, US company discovered it was, closed down the account and refuses to continue that business relationship by handing over data.
So sounds like standard policy to me. It would be like me getting banned off a game because I broke TOS (because OP did break TOS, it’s pretty much boilerplate and they have experienced this before so it’s not like they were not aware) and getting pissed off that I can not access my chat history any longer.
OP was on borrowed time from the beginning.
Does it suck? Sure it does. But what else you going to expect? For them to explicitly break the law after they discovered they were already in violation and took the steps needed to come under compliance because you didn’t read ToS, or (with them admitting this isn’t the first time they have got dinged by this law, probably the more likely) wilfully choose to ignore them.