Hi ​@Rosemount, 

We’re sorry to hear that you are unable to make or receive calls after upgrading your SIM.

Please try the following troubleshooting steps:

• Restart the handset completely
• Turn Airplane Mode ON for 60 seconds, then OFF again
• Ensure the SIM card is inserted correctly
• Check that the new SIM is showing signal bars and connected to the network
• Ensure the handset software is fully updated

Please also try manually selecting the network:

For iPhone:

• Settings
• Mobile Service
• Network Selection
• Turn Automatic OFF
• Select iD/Three manually
• Then switch Automatic back ON

For Android:

• Settings
• Connections
• Mobile Networks
• Network Operators
• Turn Select Automatically OFF
• Select iD/Three manually
• Then switch Automatic back ON

Please also:

• Ensure VoLTE/4G Calling is enabled
• Try setting the handset to 4G/LTE only temporarily
• Test the SIM in another handset if possible

If you are still unable to make or receive calls afterwards, please contact our Live Chat Team so that an agent can check whether the SIM upgrade has fully completed on the account.

Owethu