Your signature card probably gives you an option of checking "business" or "personal." I've never been able to figure out why the forms vendor puts it on the form.
If your bank never uses the distinction in decision making regarding fee schedules, transaction capabilities, due diligence monitoring, or anything else it really makes no difference which box you check or whether you check either box.
Ask yourself: In our system, what is the significance of checking one box vs. the other? If the answer is "none" then it simply doesn't make any difference.
Knowing that response would not satisfy some people, I will say that an estate or trust account isn't really a business account, but it certainly isn't opened for personal, family, or household use either. I would check the box that says "Business" and go on about mine.