I believe it was on this forum that I read to reset/erase iphone and resync but use the set up as a new iphone option. I guess the assumption is that when you sync from a back up of the old software there is some gremlin that get carried over to the new iOS and causes this.
My girlfreind had the issue and I made a call with her phone and did a basic field test with my palm covering the sensor, it seemed to work fine, but she was hanging up on me and muting herself during our calls, so she did in fact have an issue.
I did the above reset and she hasnt had an issue since. I am not implying that it is a fix, but she had the issue and now she doesn't. It is an easy task, so therefore may be worth a try.
My girlfreind had the issue and I made a call with her phone and did a basic field test with my palm covering the sensor, it seemed to work fine, but she was hanging up on me and muting herself during our calls, so she did in fact have an issue.
I did the above reset and she hasnt had an issue since. I am not implying that it is a fix, but she had the issue and now she doesn't. It is an easy task, so therefore may be worth a try.