Mistaken for being someone else here?

What or how would I do is this situation?

Out of nowhere suddenly just now, someone sent me a message...mistaking me for someone else, like someone not good and doing bad stuff to him/her.

I did then reply that I'm not that person and asking for explanation because it's clearly a huge misunderstanding...but somehow that person never gave any explanation and kept making assumptions about me which made no sense.

How do I deal with this?

I did not decide to be in SW for this.