iPhones, iMessage and FaceTime can get stuck on the temporary number when you first join giffgaff. If you've already waited past 9pm on your transfer day, try these nifty steps:
Set date and time to auto
Look under Settings > General > Date and Time. Make sure your phone's set to automatic time and date, and automatic time zone.
Reset iMessage
Turn off iMessage by going to Settings > Messages. Switch off iMessage. Turn off your phone. Wait 5-10 minutes, then turn it on again.
Go to Settings > Phone and make sure 'My Number' is set correctly. Change it if it isn't.
Turn on iMessage again. Go to Settings > Messages and toggle iMessage on.
Need further help? Try these advanced steps
Sign out of your Apple ID
Head to Settings > Messages > Send and receive, then tap your Apple ID email at the top and tap 'Sign out'.
Turn off iMessage
Head to Settings > Messages and toggle it off.
Turn iMessage back on
Go to Settings > Messages and toggle iMessage on.
Sign into your Apple ID
Head back to Settings > Messages > Send and receive, then tap 'Use your Apple ID for iMessage'.
Check your carrier settings are up to date
As a last ditch attempt, head to Settings > General > About. Just hang about on this screen for around 60 seconds. If an update to your carrier settings is available, you'll see a pop-up appear.
If nothing sorted your issue, you'll need to contact Apple Support so they can look into your issue.
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