Document everything. Write down every solution you've tried, and the result of each test. Screen shots and videos of the issues happening and the tests you've performed can trump the MacBook-based diagnostics that the Apple Genius will run on your device. Those diagnostics apparently don't accurately log failed calls, since they're not considered to be dropped calls by the software.
Try all of the standard fixes first. One common "fix" that appears to be reaching urban myth status is reseating the SIM. Give that a try. If you have another phone to test (your old iPhone, for example), see if that phone experiences the same problems in the exact same location. Try placing the phone on a flat surface to see if the calls go through when you aren't holding the device (that's the way I make 90% of my iPhone calls, by the way...). Make sure to restore your iPhone using recovery mode without restoring from backup. If you're still having problems at the end of all of this testing, then make a Genius Bar appointment. You can use the new free Apple Store app to make that appointment, if you like.
Be firm, yet polite at the Genius Bar. When you're at the Apple Store and talking with your Genius or other Apple Store employee, they may suggest that you purchase a $29 iPhone 4 Bumper to fix your reception issues. In our opinion, that's the time to firmly but politely decline to spend your hard-earned money to fix a problem caused by a product that appears to have more problems than just an issue displaying signal strength bars. Show the staff your records and screenshots, and offer to play your videos. If the Genius or store manager offers to swap out your iPhone 4, ask them if they expect a swap-out to resolve the problem. Make it clear that you want Apple to fix your issue, and that you expect to be able to place calls while holding your iPhone in your hand.
Keep in mind, you're not going to be able to just demand a free bumper. If you're uncomfortable walking into an obvious consumer rights situation or just don't have the time to go through the standard "fixes" first, you may want to simply part with the $29 and watch the issue go away. On the other hand, you've paid for a working product, and if you're well prepared, polite, and patient, you may be able to resolve the issue at no cost to you beyond an investment of time.
Genius Bar employees don't set Apple corporate policy. Apple Store managers are accountable for their inventories and revenues. It appears, however, from numerous reader anecdotes, that the bumpers are ameliorating the reception issues. In our opinion, Apple should do the right thing and just supply a bumper on request -- which would be a lot cheaper than the $100 credit offered to irate first-gen iPhone early adopters when the phone price dropped. Right now, they're not doing the corporately responsible thing -- they're making excuses instead.
We can't guarantee that you're going to find satisfaction, but if you are prepared and polite, you might just have the problem resolved at no cost to you. And, if you don't get satisfaction, Apple has waived the restocking fee if you want to return your iPhone 4. If you've been able to get a free bumper to help your iPhone 4's reception, or if you've been told by Apple that there is no problem, we'd like to hear about it. Leave your comments below.