Apple has just released iOS 7.0.4, a point update for this year's big iOS 7 software. In addition to the usual bug fixes and improvements, Apple lists a fix for hanging FaceTime calls.
As always, you can update over-the-air (OTA) and in-place - the fastest and most efficient way to do it - by going to Settings > General > Software Update on your iPhone, iPod touch, or iPad. Otherwise, you can tether up to iTunes and do a full backup, install, and restore over USB.
Once you've gotten iOS 7.0.4 up and running, let me know how it's working for you!