On my iphone 4S running iOS 8.2, There is one number in my contacts that I cannot text to. The message back says use a valid 10 digit number, which it is. I can call the number, just not text. I've tried it with and without a '1'. Any ideas?

Hello,

Thank you for participating in the Apple Support Communities.

If you're not able to send a text message to one contact, deleting and re-entering the contact is a good troubleshooting step. If you still receive a message about entering a valid ten digit number, there are more steps in this troubleshooting guide that can help:

If you can't send or receive messages on your iPhone, iPad, or iPod touch - Apple Support

Start with these tips:

Delete existing conversations

If you can't send messages to a certain recipient, delete any conversations you have with them and try sending a new message. When you delete a conversation, you won’t be able to recover it. Make sure that you take a screenshot or forward any messages that you want to keep.

Restart your device and check for updates

1. Restart your device.
2. Check for a carrier settings update.

Sincerely,

Jeremy