If you are constantly getting "call failed" but you can still receive calls and use data this might help out. I started having this problem every morning when I turned off airplane mode to start my day. One of the following usually fixes this problem. 1. Make sure the Date and Time aren't set "automatically", Manually select your home town, the phone is defaulted to Cupernico and if the phone and your service provider aren't time synced it could cause problems. 2. Turn airplane mode off/on 3. Reset Network Settings 4. Turn on "Show My caller ID" This seems to be the one that works most constantly for me if the others don't work. Seems that when you start the phone or turn off airplane mode, this option doesn't load up correctly. Hope these are helpful.