Hello there ValC8,
It sounds like you are not able to activate iMessage on your phone with your new SIM card. I recommend the troubleshooting from the following article to help you get that resolved, named:
iOS: Troubleshooting FaceTime and iMessage activation
These messages occur when your iPhone is trying to activate your phone number with iMessage or FaceTime.
To resolve these status messages, follow these steps. After each step, turn FaceTime and iMessage off and on again in Settings > Messages and Settings > FaceTime.
- Update to the latest version of iOS.
- Make sure that you have a cellular network connection with your cellular provider. You need a cellular network connection to activate iMessage and FaceTime with your iPhone phone number.
- Go to www.apple.com in Safari to make sure that you have a data connection. You need a data connection to activate iMessage and FaceTime with your iPhone phone number.
- Make sure that you can send and receive SMS. You need a valid SMS messaging plan to activate FaceTime and iMessage.
- Make sure that FaceTime hasn't been restricted: tap Settings > General > Restrictions > FaceTime.
- Set iPhone to the correct time zone: tap Settings > General > Date & Time.
Note: If Set Automatically is on but the incorrect time zone appears, turn Set Automatically off and choose the correct time zone, date, and time.
- Contact your carrier to verify that there are no restrictions, blocks, or filters on text messages. Restrictions, blocks, or filters on text messaging will prevent iMessage and FaceTime registration from completing.
If "Waiting for Activation" still appears after you perform these steps, turn FaceTime and iMessage off and on in Settings > Messages and Settings > FaceTime. You may need to wait up to 24 hours to complete activation. Most attempts will take less than an hour, but some attempts may take up to 24 hours. If your issue isn't resolved after 24 hours, please contact Apple for assistance. If you've recently performed a remote wipe on your iPhone, wait 24 hours from the time you performed the remote wipe, and then turn iMessage off then back on.
You can still activate iMessage and FaceTime with your Apple ID when these status messages appear. You can see that you've activated FaceTime and iMessage with your Apple ID by tapping:
- Settings > FaceTime > You can be reached by FaceTime at:
- Settings > Messages > Send & Receive > You can be reached by iMessage at:
Thank you for using Apple Support Communities.
All the best,
Sterling