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. Go to Settings. Scroll down and tap on 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.
If that hasn't worked, 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.
Restart your phone.
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 for a quick response. Or ask one of our helpful agents for an answer within 24 hours.