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.
Extra help steps
If these haven't worked, try these advanced steps below:
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.
Did this solve your problem? If not, pop over to our friendly community or chat with our giffgaff HelpBot for a quick answer.