The only time the sound/speaker and mic don't work is when I answer or make a call

Question

The only time the sound/speaker and mic don't work is when I answer or make a call. They both work fine for everything else. This has been going on for over a month. AT&T said it's Apple and Apple said it's AT&T. I've been around that cycle twice. 
When I dial a call, I can see the status words on the screen but can't hear the ringing. If the person I'm calling answers, my screen will show the call was connected and the call timer will begin but I can't hear anything and they can't hear me. If one of us doesn't end the call, the timer keeps going and I'm being 'charged' for dead air. (Of course, one of us disconnects so mins/cost isn't an issue, I'm just adding the info in case it helps solve the problem.) If they don't answer, the call will go to their greeting but I can't hear it and wouldn't be able to leave a message anyway because my voice isn't going through. However, they will get a voice mail alert and see that I called but no message was recorded.
If some one tries to call me they will hear ringing but when I answer, they can't hear me and I can't hear them. If I don't answer, they will hear my greeting and can leave a message. I can retrieve and hear my voice mail. Trying speaker phone and headsets didn't change anything for calls out nor for calls in. 
I have 4.3.3 and have synched, reset, rebooted, turned things on and off and off and on and took the SIM card out of the phone and out of it's tray and put it back in. I've done all that several times in just about every combination and order possible. 
Hopefully the following will provide good clues:  On only about three of the many attempts I've made to get it to work correctly that included taking out the SIM card, I could make and/or get one or two calls with no trouble but then the problem comes back. Also, when I swapped the SIM card with another iPhone4 on my plan, the other phone would work with my SIM card but my phone still would not work with the other SIM card. The last fact makes me think it is an Apple issue. I'll go to an Apple store (genius) this weekend. Will I be wasting my time and gas? Anybody have any experience with this problem?

Answer 1

Let me try and address some of your questions.  I'm only on a pc, so a few of these answers might be slightly different on a Mac, but not too different (such as control click rather than right click).
First, when you buy something on your phone, be it apps or music, it's transferred from your phone to your Mac when you sync your phone.  So those apps should now be in you iTunes library. ( IF for some reason you can't find them there, you should be able to download them again, either onto your phone or through iTunes.  On your phone, go to the App Store > Updates and you'll see a "Purchased" link at the top of the page, you can view all purchased apps here and redownload them.  In iTunes, you can go to Store > Check for available downloads. )
Whenever you plug your phone in, it should create a backup of everything you have on the phone.  This is how, provided restoring your phone as a new device doesn't fix the issue (more on this later), you can put all of your music and apps onto the new phone.  You can always plug your phone into your Mac and the first thing it should do when it syncs is create a backup.   If you want to be sure, you can right click on your device in iTunes (on a pc) or I assume control click on a Mac and select "backup".
The genius will take care of the sim card and setting up your phone, however you will have to put all of your music and apps on it, unless you ask the genius, I've never bothered since I know how to do this.
You should have no problems restoring from a backup if they give you a new phone.  However, it's probably safest to try and create a backup of your last phone backup before you restore it as a new device.   I suggest you refer to http://support.apple.com/kb/ht1414 for more information about that.
I've had no problems with my new phone so far.
I'll try to keep checking this thread if you have any other questions or need more clarification.
Edit: I should say we never did figure out what exactly was wrong with my phone.  The only thing I can think of was that it got a lot hotter than the phone it replaced, and also the phone I just got yesterday to replace the malfunctioning one.  But otherwise they saw no problems with the hardware, but acknowledged it must have been the hardware since we tried everything else.  Also I would go with a list of all the things you tried with this phone, for your own reference and the genius's, especially if you're not confident in your tech skills Showing the genius that you've tried: different sim cards, updating the software, restoring it from a backup, and now restoring it as a new device, should convince them that you've done everything you could, and the only other answer is hardware problem.
Also if you don't already have one, make a genius appointment ASAP.  Most stores are very busy and their appointments fill up fast.  I always suggest making an appointment as early as possible, hopefully before the retail store hours when they've only got techs there because they usually are less stressed and have a bit more time to spend with you.  The easiest way to make an appointment is to download the Apple Store app.  It detects the closest Apple store from you and makes it quite easy to schedule a genius.
Message was edited by: deddinty