Available on Google Play: https://play.google.com/store/apps/details?id=com.liam_w.phonenumberfix
This app allows the user to change the phone number stored in their SIM card for display purposes. Sometimes this number becomes incorrect, or isn't present at all.
To do this, it utilises the Xposed framework.
This open version doesn't include the IAB components (for donations). It also doesn't contain the icon used on the Google Play version for licensing reasons.
Feel free to open pull requests/issues. I'll merge them into the Google Play version if they're worthwhile (with credit, of course).