Why does my iPhone 5 have poor reception in my office?

I have gone from a iPhone 4 to an iPhone 5, and lately whenever I go in my office i can't hear the conversation that I'm having, but as soon as I step outside my office I can hear the person talking fine. I need to be able to sit in my office and talk to people with my computer screen in front of me and I can't do that at the moment. I must also add that I live in a small town and work from home, so my office isn't like on of the ones in the city, its just a small room outside.

Low signal