I'll be sitting on my couch using my phone not really moving to much and my signal bars go up and down. Sometimes I'll have full bars, then two will drop off, then a couple minutes later they'll come back. I never noticed this on any of my other phones, but I never really used them as much as I use this one. Also, sometimes I'll have lime one bar, I'll shut my phone off and turn it back n and I'll end up with a few more bars. Is this normal or could there be an issue?