Thanks for posting the Apple Support Community. I understand that you're having trouble with your iPhone continually hanging up while you're trying to dial out to make a call. Being able to use your phone when needed is important and I'm happy to help.
If you haven't already, I recommend to try closing out of the Phone app, then restart the iPhone and test the issue again.
Force an app to close on your iPhone, iPad, or iPod touch
Restart your iPhone, iPad, or iPod touch
If you're still having trouble with this happening after restarting, then I recommend to reinstall iOS on your iPhone. This should not affect any of your data, but it is always a best practice to make sure you have a current backup in either iTunes or iCloud. How to back up your iPhone, iPad, and iPod touch
Once you have a current backup, follow the steps in the section titled "If your device turns on but gets stuck during start up" from the following article. These steps will reinstall iOS. Keep in mind that these steps were written for a different issue, but they will still help us isolate the situation further. If your iPhone, iPad, or iPod touch won't turn on or is frozen