I found the following on click here
Problem: When I finish a call and hang up, within 2 seconds, the phone is dialing the last phone number again.
Solution: Before doing any troubleshooting make sure that your phone is running on the latest software version. To be sure try to manually check for any update and install it if necessary.
Follow the steps listed below to troubleshoot the issue.
Clear the cache and data of the phone app from the application manager. In some cases, corrupt temporary data of the phone app can cause this problem and getting rid of the temporary data of the app works.
Go to Settings – Motion – Direct call then make sure call currently displayed on screen is “off”
Start the phone in Safe Mode then check if the issue occurs. If it doesn’t then a third party app could be causing this. Find out what this app is and uninstall it.
Wipe the cache partition of your phone from the recovery mode. This clears the temporary data of the phone system and usually works in this case.
Backup your phone data then do a factory reset.