I cannot reject call when the phone is locked.. below is what i google.. for sharing.. so many "new features"... till most confused..
https://discussions.apple.com/thread/5322040?start=30&tstart=0
Till iOS 7, the past iOS' had an option to reject an incoming call (by swiping up) when the iPhone is locked. And there would not be a reminder to the missed calls except the display in 'Notification Center'. This was a point of concern raised by several users, to include default remainder when a call is rejected.
From iOS7, by design, 'Remind Me' functionality replaces 'Reject' when a locked iPhone gets an incoming call. 'Remind Me' acts as 'Reject' + 'Reminder'. It first rejects the call and adds a reminder to call the appropriate recepient.
However, there would be a 'Reject' button when there is an incoming call while the iPhone is not locked. The idea is simple here. An iPhone that's not locked is in use by the user and the user cannot accidentally click anything. Hence when someone intentionally tries to reject, they can touch the 'Reject' button. Alternatively 'Remind Me' holds good too.
This would not be comfortable for those who gets annoying calls from unknown numbers, however this feature makes a lot of sense for those who intentionally rejects valid calls.
I don't see Apple engineers would work a fix on this as claimed by many here.
I also don't think if Jobs is alive, he would had a say in it. Quite funny when Steve Jobs' death is felt for missing functionalities.