I'll get downvoted but whatever. You're in a huge company in a corporate environment, therefore there is no tactful way that is guaranteed to not backfire, the

I'll get downvoted but whatever. You're in a huge company in a corporate environment, therefore there is no tactful way that is guaranteed to not backfire, there is only the corporate way: 1. Document all instances where it happens. Don't name names. 2. Go talk to your manager about it (even without the list of events, that's ok). 3. If nothing is being done, raise an HR complaint with your list of evidence, insisting on the fact that YOU feel discriminated against and that you are in a hostile work environment. If your coworkers already aren't speaking in English when you're around, they won't start just because you ask, at least not long term. Note the goal here is not to blame others, it's to get what you want.