At a previous job (Microsoft shop but in the public sector so 10 years behind), the standard messenger when I started was Skype for Business.
In case you’ve never used Skype for Business, it’s “Skype” in branding only and actually has nothing to do with the Skype software that Microsoft purchased and is more like MSN Messenger.
Compared to that, Teams is a huge step up.
Also, at a Microsoft shop, you have to use what Microsoft provides even though it’s usually balls.
It’s 90% of the reason I now refuse to work anywhere that’s bought into the Microsoft ecosystem. It’s just so… mediocre