I had a legal name change through a probate court. Each State is different and you should find out. Once I had the form, I went to DMV and SSS to update my information. I tried calling USCIS, but their customer service had no idea what I was attempting to explain to them thus, I wrote them a letter explaining the name change and a copy of the name change form.

I guess if I wanted to, I could file for another EAD, but then again that is pretty costly. Oh, for those wondering I drop my second last name.