[AngelicaDeAlquezar]

I agree with Poli, but I'll add a note:
"Pillar" is a verb mostly used in Spain. In Mexico, for example, we'd never use that.
"Coger", is a no-no in Mexico, and we might use "atrapar" or "agarrar" instead.
All of these verbs are synonymous, but only when you mean "to seize", "to grab", "to catch".

In the case of your example, we'd prefer another construction like "te equivocaste de persona", or something more explicit like "estás culpando a la persona equivocada".