You must start a text conversation with the unwanted contact, then you will be able to edit contact/delete.
Another way to do this is as follows.
You will have to restore the iPhone to a base firmware install, which will erase everything on the iPhone, but you can later restore the contents of the iPhone to a backup that you have on the computer (the same computer you used in the past to sync the phone with):
- You will need to have the iTunes application installed first. If you do not have it, you can download it for free from the following site: http://www.apple.com/itunes/download/
- Press and hold the top power button until the iPhone turns off
- Connect the iPhone to the computer that you have been using the phone and iTunes with
- Hold down the HOME button on the front while pressing the Power button (continue holding the home button)
- Continue to hold the HOME button until you see the "Connected to iTunes" messageOption 1:
In the Summary tab, click Restore and follow the prompts. (THIS WILL ERASE everything on the iPhone and make it just as it was when you first purchased the phone).Option 2:
Click the button on the top right of the iTunes window for your (iPhone) and then click the Restore button.
- Once that is complete, right click the iPhone listing in the left panel of the iTunes window
- Choose "Restore from Backup"
- Choose a backup date and restore.
Now your iPhone will be back up and have all the restored information from your last sync.