Q: Iphone 4 people cant hear me during calls.

Apple cant "fix it" as they do not know the origination of the issue. If you are referring to replacing the phone as the "fix" then yes.

Working at Last

Well I hate to say it but I too was having the same problem.  Tried multiple fixes, rebooting restoring and others.  I loved the turning off the 3G one the best, since I'm in Okinawa, Japan and all I have is 3G.  My phone has been having this issue off and on for the last few weeks now.  Was nice to see I was not the only one having this problem.  But I am some what happy to report that I think I fixed the problem.  After spending most of the day reading the posts, I tried first cleaning the headset jack with both canned air and plugging and unplugging a headset in.  I then deleted all running aps I had  running in the background, by double tapping the Home key.  I had just about every ap open in the background.  Once both steps were done I placed a test call to a friend and bingo it worked.  Not sure which step fixed it but for now I am happy. 

I am still disappointed in what seems to be a lack of interest on Apple's part to try and resolve the problem.  This was my first Apple device and most likely when I get back to the states it will be my last.  I'm still surprised no one has mentioned taking Apple to court on this yet.  Selling a product and not having it work in its primary function is unsat.  I should have known better since the Iphone seems to be the only phone you can not get insurence on.  Why can't Apple stand behind their products?

Same problem here. Started only a few days ago with no noticable changes made to anything to cause it to happen. I'm reluctant to do a full restore, but I have a genius appointment this weekend so will see what happens then.

Well I spoke to soon.  After only 1.5 calls my phone revered back to the all popular iBrick.   Now thinking that the whole plugging and unplugging from headphone jack was not part of the solution as I use a jack in my car all the time.  I am starting to believe this is software based problem.  Skype works fine and so does the voice recorder.  Unless this deals with just the noise reduction speaker, but I don't see that as a possible problem since I was able to get phone working for a short time and I didn't tamper with anything or disassemble anything.  I am thinking this is dealing with the memory.  Much like how computers can run low on virtual memory I think the same is happening to the phones.  Also since reading the posts most people have sent theirs back to to be returned because no problem was found.  I think Apple needs to see this as a valid problem for their customers.  Time to consult their support.

Another update:   PLEASE READ IF YOU WARRANTY HAS EXPIRED.     I filed a claim with AMEX and they paid.   It was only 300 (the amount actually paid), but still... better than the Apple alternative.   Now the delimma, pitch in an additional 300 and get a new, potenitally defective phone or wait?

Oh and by the way, problem getting worse.   I was on the phone with my brother this morning for 5 minutes and phone went out three times.   I BRICK !!!

Double clicking the home button to turn off apps running in the bavckground got my microphone to work again. I tested it by making a voice memo, which was not working at all when I had the problem of people now hearing me during phone calls. Thanks. Hope Apple does the right thing and fixes this glitch.

I was having this problem for about a week, banging the phone on the table during calls was working but got extremely annoying after about the 3rd time in a call.  I went to the genius bar, they ran some diagnostics which turned up fine and gave me a new phone.  They did say a lot of people were coming in with this problem though...

Took the phone in to the Apple store, walked out with a replacement phone. They have obviously received a lot of returns over this, as there were no questions asked.

Seems this is this best solution, particularly if your phone is still under warranty.

Another Update - I was in Apple store again this morning to purchase a new phone.  (If you haven't been following.  I was there about a week ago and they told me it was out of warranty and they couldn't help me, other than to purchase a new phone.   I then filed an extended warranty claim with my AMEX which was paid this week)  I told the guy about my issue and why I was getting a new phone.   He took me back to the Genius Bar and replaced my phone for FREE !!   And, my warranty had expired by 17 days.   He would not fess up and say that it was a known issue, but he did say that he's seen the problem before.   This guy ROCKED !!    In and Out in 20 minutes.   Now, I've got to let AMEX know...can't use my phone in prison because I've been arrested for insurance fraud.  

The problem fix is at ifixit! Its a loose ground! Solution is to open iPhone via backplate and screw/unscrew the three grounds to the antennae they specify the one next to the camera but just to be sure do all three! It worked for me! Try it!! http://www.ifixit.com/Answers/View/38137/Microphone+not+working+when+making-rece iving+calls

ggrrrrr my i phone 4 has just started doing this i dont wanna do a restore cuz the last time i did one with my old 3g it made it slow as ****!! i guess i best get to the apple store ! but then again if they give me a replacement whats to say the same wont happen to that one ?? !!!!!

An update;

I went into the Apple Store yesterday for my third phone.

It was 20 days after my original warranty expired but since they had replaced my phone a couple of months ago I was give a ninty day extention from the replacement date.

What was funny was I don't think the genius noticed the last repacement because he said; "your phone is 20 days out of warranty but I'm still going to give you a replacement".

I think that they are told when a phone comes in with this issue to just replace it no questions asked.

After I received my phone I asked if I should set it up as new phone of resore from backup. I also asked if the problem was software or hardware. He first nodded that it was a software issue then did a one eighty and said it was a hardware one, so who knows.

If you have this problem go into the Apple Store and get them to give you a new phone.

Wow!! I'm relieved to know that it's not just me or my phone with this issue.  I started having this problem two weeks ago and since that time frame my Iphone is used exclusively as a texting phone (very dissapointed with Apple).  Anyways what is the best direction I should take since I purchase phone thru Best Buy store? Like Princess Lei would say "You are my only hope":(

i dont suppose it matters where u got it from, it should still be covered by warranty, make an appointment at the genius bar n they should replace it . i walked out with a brand new one last thursday .

I just got back from Apple store in Manhattan Beach and walked away with a new iphone.  The young lady was very friendly and within five minutes I had a new phone.  As far as the issue goes they could not give me a straight answer but only speculations.  Im very happy with the customer service at the store and will continue to be a loyal Apple consumer!!:)