If you go to your Manage Connections you should see Mobile Network, and Wi-Fi as selections. If both have a green check mark it means your getting a good signal from both and Edge is winning out on providing your phone service. You can get your UMA back in a few different ways. One is to uncheck Mobil Network while you are in a place you want to make sure you are using UMA; like home. This is what I have to do most of the time. Another way is to go to the "Mobile Network Options" in the same screen and set the "Connection Preference to Wi-Fi Only. I don't do this because is takes a lot more steps to go back to Edge when I leave the house.

On some days I can leave all checked and the phone will pick up UMA upper case just fine and some days all I get is EDGE upper case. So this was my fix and it works for me. Just my 2 cents.