Cancel FaceTime before call connects

The other day I missed a FaceTime call from my granddaughter. Later in the evening, I noticed the missed call on iphone and when I touched it, the call began to ring. There didn't seem to be anyway to stop the call before it connected. This was @ 10pm and the call was to my daughter, so we could laugh it off, but what if it was to someone else at a very Inopportune time? How can I quickly disconnect before it rings or before the other party picks up?

I missed one too and I believe I went to "Phone", tapped "Missed" and then tapped edit, and tapped delete. But if you tap a missed phone call or Face Time call, it will try to connect even if your phone is locked.

As far as stopping the call before it connects, you should be able to end the call. (Best way to do that real fast is push the sleep wake button on the top of the phone.) But sometimes that may not be possible if the call goes through real fast.