Unable to make phone call out

Since upgrade to iOS 8 I have experienced an intermittent problem when trying to make a phone call on my iPhone 5 - the green call button will not make the call. I have to turn the phone off and restart. This has occurred 3 times.

Also I had an issue with the timer not being able to be turned off - the bell at the end of the time kept on ringing and the only was to shut it off was to turn the phone off.

Can anyone explain or have similar issues?