Phone number greyed out after downloading iOS 8

Hi gingergirl18,

I have an article for you here that will help you address this issue with iMessage:

iOS and OS X: Link your phone number and Apple ID for use with FaceTime and iMessage

http://support.apple.com/kb/HT5538

Phone number missing on iPad or iPod touch

If your phone number isn't listed on an iPod touch or iPad, follow these steps:

1. Update to the latest version of iOS.
2. Verify that you're using the same Apple ID that you're using on your iPhone.
3. On your iPad or iPod touch, sign out of your Apple ID in the following locations:
   • Settings > Messages > Send & Receive. Tap your Apple ID, then tap Sign Out.
   • Settings > FaceTime. Tap your Apple ID, then tap Sign Out.
4. Sign in to your Apple ID with FaceTime and iMessage.

If your phone number still isn't listed, follow these steps:

1. Sign out of your Apple ID on all iOS devices, including your iPhone, in the following locations:
   • Settings > Messages > Send & Receive. Tap your Apple ID, then tap Sign Out.
   • Settings > FaceTime. Tap your Apple ID, then tap Sign Out.
2. Sign in to your Apple ID on your iPhone.
3. When activation is complete, your Apple ID and all verified email addresses should be visible in Settings > Messages > Receive At and Settings > FaceTime.
4. Sign in to your Apple ID on your other iOS devices.

You may also want to see the information in this post that explains some further troubleshooting steps regarding this issue:

My messaging app on my OS X Mavericks is discon... | Apple Support Communities

https://discussions.apple.com/thread/5736894

Take care, and thanks for visiting the Apple Support Communities.

Cheers,

Braden

I had the exact same problem. I "believe" I've just resolved it by turning off and then on again the top-most menu in Messages - where it says "iMessage." I turned it off, waited a moment, turned it back on again and now the phone number is reassociated with my iMessages account.

That worked for me. Something has gone screwy cuz this happened on my wife's phone as well.

This did not address the question.