After a few replacements of the same make/model failing for the same reason (3 or more orders) you can request a different make and model. They will generally do it. I work android tech support/warranty.
Go into your settings> application manager or apps > swipe to all. From there you will want to find the app you use to access the Internet. Most people just use the Internet app. When you find it clear the cache and data.
Hello! I created an AC account just to reply to your post when I was scrolling through my news stand this morning. You are definitely not the only one with dropped calls and reception issues on the newer samsung devices with the AT&T network. I actually work in the android tech support...