Question about contacts

I like my contacts to be in my phone under the First name section-for example I will put JOHN SMITH (all caps) under the first name category in the address book and I've been doing this since the first iphone and it has looked the way I want it to. I got a replacement 4S a few months ago and some of the contacts show the person's last name as well so I will get JOHN SMITH Smith in my address book. I realized that these people are ones that I email and the name that they use in their email address gets merged into my address book. This never happened and I may have tweaked a setting when I set my replacement phone up. Does anyone know how to fix this? Thanks