I just added my phone number to my iPad and now my iPhone says 'no service'?

Hello christinafromwhitecourt,

Thanks for using Apple Support Communities.

To resolve this issue of "No Service" appearing on your iPhone, please follow the steps below:

1. Toggle airplane mode: Tap Settings > Enable Airplane Mode, wait five seconds, then turn off airplane mode.
2. Turn your iPhone off, then on again.
3. Remove the SIM card and verify that it's a valid, carrier-manufactured SIM. Also verify that it isn't damaged, worn, or modified. Then reinsert it.
4. Check for a carrier-settings update. Connect to a Wi-Fi network. Then tap Settings > General > About. If an update is available, iOS will ask you if you want to install it. If Wi-Fi isn't available, connect your device to iTunes.
5. Update your iPhone to the latest version of iOS.
6. Reset network settings by tapping Settings > General > Reset > Reset Network Settings. This will reset all network settings, including Bluetooth pairing records, Wi-Fi passwords, VPN, and APN settings.
7. Restore the iPhone.

If you're outside the United States, please also follow these steps:

1. Go to Settings > Carrier > Automatic.
   If the phone registers any carrier network, Settings > Carrier will be present.
2. If the Carrier option is missing in Settings and you're outside of the Unites States, please contact Apple for support and service options.
3. Set the option for Automatic to off.
   A list of potentially available carriers appears after about two minutes. If the device is locked to a carrier, it may connect only to the carrier network to which it is locked. If the device displays carrier networks, then the device is working as expected.
4. Set Settings > Carrier > Automatic back to on.

If you're still experiencing No Service issues, contact your carrier to check for any network or account issues that could cause these symptoms.

iPhone: Troubleshooting No Service

http://support.apple.com/kb/ts4429

Take care,

Alex H.