Can I boost my signal on an iphone 4?

I usually use UMA which basically means I run my calls via my Wi-Fi, Because there's very little signal where i live. I just bought an iphone 4 and found that it doesn't have UMA which leaves me a bit stuck /! Is there anything i can do or buy to boost the signal?

Go to a place with strong signal dumba$$

Not really know but with the iphone 4 if you cover the bottom left hand side of the phone it will limit your signal because the arieal is around the outside of the phone unlike most phones