Confused first time iPhone user!

[cannoli]

My husband and I just purchased our first iPhones (4s) yesterday. I upgraded to iOS 6 shortly after I got the phone but my husband did not. Today my phone kept losing service in our apartment, but my husbands was just fine. So he called Verizon and talked to several people, and everything they told him to do wouldn't work. My phone wouldn't receive or make calls. Finally they told him we would have to go back to Verizon and exchange my iPhone for a new one. So we did that and everything was working just fine until we got back up to our apartment. The phone will make and receive calls and texts when I'm outside of our apartment, but right when I come back inside to our apartment calls or texts won't work at all. I can use the internet though and youtube and things like that. My husbands phone is just fine though. What could be causing this issue?

 

[Primetime]

Go into settings, general, reset, reset all settings. Try that.