Several users have reported problems when trying to make a call. The reported problems include, but are not limited to, call failing and no sound.
Fix
There has been similar Siri related problems with outgoing calls where there is no sound while a connection is established. It has been reported that updating to the latest iOS fixes this problem.
If you have a call failing issue and updating your iOS does not fix your problem, try each of these steps until you resolve your issue:
- Make sure that you are in range of the cell network by checking cell signal indicator bars.
- Reset your network by tapping Settings > General > Network
- Reset your iPhone by holding down the sleep and home buttons until the Apple logo appears
- Try Settings > phone > show my caller ID. Just visit and let the device load your settings.
- Try disabling airline mode.
Nicholas on 
Lawrence Alonzo on 
rickyc on 
Carnghamcats on 
Deb Santagata on 
MARK on 
Shafqat Zaman on 
AppleID:( on 
March 20, 2012 at 8:27 PM
Hi… Still no luck !! Plz help me… still call failed !!
April 18, 2012 at 10:14 AM
Same here.
The phone was working fine until yesterday. Outgoing calls Failing with error “Call Failed”.
Earlier the phone was not working at all. No Outgoing. People calling me could hear the ring, but the phone at my end was not ringing. I updated the Firmware to 5.1 and I started getting incoming calls and SMS started to work.
I finally restored the phone, yet no luck.
The only thing what I did yesterday was I checked a friend’s New Micro SIM in my phone.
Any suggestions
???
Thanks
April 29, 2012 at 6:45 AM
If the Show My Caller ID option inactive, you cannot change this option for some reasons. You can use cydia tweak called Caller ID SBSettings Toggle to change caller ID option on iPhone.
This works for Me