Except I don't use SLACK
First of all, "slack" is an inside joke about the church of the sub-genius, with "Bob" Dobbs. That's a bunch of nitwits and I'm not stooping to that level. (Same goes for "slackware linux," bunch of shmucks yes a'la alfred e neuman.)
Second of all, Microsoft harassed me one time too many to "sign in to keep using microsoft teams." You know what happens if you stop signing in to keep using microsoft teams? You can stop using that stupid thing. Which is nothing but a rehashed crappy version of "Skype," with all the same echo and crash problems it ever had. Let's put it this way: I clearly recognize "test call" as being identical.
You know what works just as flawlessly as it ever has? That would be my SPA2102 "voip" adapter and my e-mail account. If you can't talk to me on the 'phone and you can't send me information via e-mail, then I guess you & I just don't have anything to discuss.