An iPhone, like any other mobile phone, keeps track of all of your recent incoming, outgoing and missed calls. Follow the steps below to delete missed calls.
Tap the "Phone" icon on the lower-left corner on your screen. On the Home screen Phone icon, number of missed calls are listed there in red.
Tap the "Recents" icon at the bottom of the screen and tap on "Missed." You can then view a list of the calls which you have missed.
Tap on "Clear" to remove all your missed calls.
Please note that you cannot delete individual missed calls unless if you use a third-party application. Apple has designed the iPhone so that the entire phone-call list must be deleted.