Check that your mobile has the right 'SMS Centre Number'. Without it, you won't be able to text:
- From Start, flick left to the App list
- Scroll down to Messaging and then click on it
- Click on the 3 dots in the bottom right-hand corner of the screen
- Click Settings
- Check the SMS Centre Number field. It should show +447785014311. If it doesn't, click in the field and change the number displayed to the correct one.
- Click Save
You should now be able to send texts.