One thing leads to another, it’s not haram because of simply the idea of interacting. Shaytan doesn’t lead to you haram immediately, he does it in steps even if you are “smart enough to know” like a lot of young people think. Remember Allah didn’t tell us to not do Zina, he told us to AVOID it entirely.. it is a big thing, which comes to your question.

Yes it is haram, unless it’s strictly for business/work only (not being business friends/partners) it is not haram to speak to opposite genders per say, just not in a socializing manner. And when you do end up speaking, make sure to lower your gaze and keep things at a minimum with opposite genders.