Client calls me by the wrong name. Can I correct him?

I’m a 28-year-old woman with a small freelance business. One of my smaller but loyal clients continuously calls me by the wrong name in-person and via text/email and I’m not sure how to correct him.

My boyfriend advises me that I shouldn’t set him straight because his “money is green” and he pays me in cash but it frustrates me to end! Especially since my name is on my business card, my email address and my email signature. Is there a tactful way to correct him without alienating him?