iPhone 4S good computer but has Worst Reception

I use iOS 5.1 and this is my first iPhone 4S.

As a computer this is a good device but....

the reception for the Phone is bad, many missed calls.

At work the reception signal is weak (concrete building) but had no problem with OLD smartphone (not a iPhone).

Things get worst, I had 3 receiving bars  on 4S, I called on the fix phone to my own iPhone while I was watching the iPhone. And it was voice mail even if I saw 3 receiving bars on it !!

Thus even if the iPhone says you have reception (3 bars) this is'nt always the through. The bars are maybe to slow to display?

I think I will bring this iPhone back because I can't use it as a telephone :-( the Nokia Lumia 800 has maybe some bugs, but you can call with this telephone :-)

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Other (data) reception problem: I was traveling in the train, and there was no reception. Sow far, normal. Then the whole ride no reception for data (phone reception worked well).

After the ride still no data reception ! This was at a point that I know there was 3G reception. Then I remembering a same story on the internet about this problem (a iOS 5.1 problem).

I rebooted the iPhone and then I had 3G on the same spot ! The problem is the iPhone, I don't know if this problem caused by iOS5.1 or the hardware.

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Hopefully someone read this by apple staff and do the nessecery things. I would appriciate if they contact me about that. I am an electronics engineer.