Just adding my 2 cents to this issue.
iPhone 5S / iOS7.02
Also having issues when recieving calls, having my face/cheek/ear push buttons, and its getting very annoying. I have searched and tried all suggestions listed in this post, with no luck.
I do seem to agree with SenorDD in terms of it happening mostly with incoming calls, yet I have notcied it a few times with outgoing as well.
Apple needs to fix this, I believe this product is an iPHONE!!!! and its the phone part that really needs to work. I love iOS 7 but it drive me crazy when they take features that worked fine in previous versions and F with them.
Come On Apple.. This one should have never got past all the Beta Releases, not to mention that the whole (Compass / Level - Gryoscope) issue also needs to be corrected ASAP.. I will never use the level or compass app, but when it starts affecting games, maps, etc that is a major issue..