Q: My number is "Unknown", Can I add it?

Settings>Mail, Contacts, Calendar>go to Contacts section>my info

Try resetting your network settings. Settings>General>Reset>Reset Network Settings

Open phone app, tap the middle tab (contacts), look at the top of the list. Can you tap there to change from Unkown to your number.

If not try to remove and insert back your SIM.

OK. If possible, try to get hold of another sim card from the same carrier, put that in your phone and see if the phone number assigned to that sim card appears under Settings-Phone. This will help you determine whether the issue is with your phone or your sim card. If the number appears - get yourself a new sim card. Otherwise, take the phone to an Apple retailer or Genius Bar

There could also have been a problem when you first activated your iPhone. This would be resolved by an iTunes restore followed by re-activating your phone either through iTunes or on the device itself. Do remember to backup your data and settings first, though, in case things go south.

carlvii is right. Settings>phone>change it manual.

Yes, my phone number shows up under Settings>Phone and I am able to change it to anything I want. For instance, I just changed it to "911" to see if that would work

This is obviously an issue with your carrier, then. Which carrier are you on?

If your phone is unlocked, you might want to try inserting a sim card from another carrier - at which point the phone number of that sim should show up in Settings>Phone and you would then be able to change it to your actual phone number, and then put your original sim card back in. Long shot, but it might work...

I have an iPhone5 with Verizon and it solved my problem.  Thanks

I cannot edit.. The My Number  Unknown is grayed and cannot edit.

I am in Australia and using Lycamobile