iPhone 4 reboot when making phone call

[sqa4life]

Hi All,
I am new here. I am having a few issues with my iPhone 4 and I need help.

I got my iPhone 4 a few weeks ago and it has been great until last week. -The phone reboot itself when I make a call. Sometime I was able to make a few calls after the reboot, then the issue came back again.
-Now, it started rebooting when I receive calls as well.
-The signal bar started decreasing if I hold the phone at the lower end (near the home button)

I have the latest firmware and yes, I restored the phone a few times with no 3rd party app on it, no luck.

any thought?

 

[bab2010]

Take it to the apple store if you restore and the trouble is still there.