How do I change my legal name with Xfinity?

I've been on Xfinity chat assistant several times about this issue so I figured I'd try this. I changed my name on my account, but my former name is still showing up on contracts so this leads me to believe I only changed my "preferred name" in the system and that's different from a "legal name." This change was legal, so how do I go about having that reflected on all aspects of my account? Thank you.