Help Center
Quick Links
I activated my SIM but the service is not working. What can I do?
If you have activated your SIM in your Tello account but the service still does not work on your device, there are a few steps you need to follow in order to check the activation completed correctly.
1. Check the SIM/eSIM
For further inquiries about activating the eSIM, please check the "How can I activate my Tello eSIM?" section.
2. SIM Error "Invalid SIM" or similar.
If your phone says "Invalid SIM," "Network Unlock PIN,", "SIM Locked," or similar messages, your phone is likely locked to your previous carrier.
On iPhones, you can also check this by going to Settings> General > About > Carrier Lock. SIM Locked means the device is carrier locked.
To unlock the device or verify the lock status you will need to contact the provider of the phone.
If the issue persists please follow the steps below:
1. Software & Network Settings
Check that your device has the latest software version installed.
2. Enable VoLTE: This is required for calls.
Android: Go to Settings > Connections/Network & Internet > Mobile Networks
If you have an option for VoLTE, make sure it's ON (In some models this option can also be named: Enhanced 4G, HD Calls or similar)
iOS: Tap Settings > General > Cellular (or Mobile Data) > Ensure the Cellular Data switch is in the "ON" position.
Tap Cellular Data Options > Tap Voice & Data.
Ensure LTE is selected.
Ensure the VoLTE slider is in the "ON" position.
3. APN check
4. Reset Network Settings
If the steps above don't work, try a network reset.
Note: This will also clear your saved Wi-Fi passwords and Bluetooth pairings.
Android: Go to Settings > General Management or System > Reset options > Reset Network Settings (Reset Mobile, Wi-Fi and Bluetooth)
Reboot your device and test the service.
iOS: Tap Settings > General > Reset or Transfer > Reset > Reset Network Settings.
Enter your passcode and wait for the device to restart on its own.
Test the service
⚠️ Warning
Before resetting network settings, make sure you know your Wi-Fi passwords, as you will need to reconnect to them afterward.
Next Steps
If the service is still not working properly after doing these checks and trying these steps then email us with the following information:
1. Check the SIM/eSIM
- Physical SIM: Power OFF your phone, remove the SIM, and make sure it’s seated correctly in the tray.
Alternatively, you can also check this guide on our blog. - eSIM: Simply restart your phone. Then, go to your settings and ensure the Tello eSIM is toggled ON.
- Android: Settings > Connections/ Network & Internet > SIM Manager/ SIMs > check the Tello eSIM is ON.
- iOS: Settings > Cellular > Under the SIMs section, check the Tello eSIM is ON.
For further inquiries about activating the eSIM, please check the "How can I activate my Tello eSIM?" section.
2. SIM Error "Invalid SIM" or similar.
If your phone says "Invalid SIM," "Network Unlock PIN,", "SIM Locked," or similar messages, your phone is likely locked to your previous carrier.
On iPhones, you can also check this by going to Settings> General > About > Carrier Lock. SIM Locked means the device is carrier locked.
To unlock the device or verify the lock status you will need to contact the provider of the phone.
If the issue persists please follow the steps below:
1. Software & Network Settings
Check that your device has the latest software version installed.
- Android: Tap Settings > System > Software Update.
- iOS: Tap Settings > General > Software Update.
2. Enable VoLTE: This is required for calls.
Android: Go to Settings > Connections/Network & Internet > Mobile Networks
If you have an option for VoLTE, make sure it's ON (In some models this option can also be named: Enhanced 4G, HD Calls or similar)
iOS: Tap Settings > General > Cellular (or Mobile Data) > Ensure the Cellular Data switch is in the "ON" position.
Tap Cellular Data Options > Tap Voice & Data.
Ensure LTE is selected.
Ensure the VoLTE slider is in the "ON" position.
3. APN check
4. Reset Network Settings
If the steps above don't work, try a network reset.
Note: This will also clear your saved Wi-Fi passwords and Bluetooth pairings.
Android: Go to Settings > General Management or System > Reset options > Reset Network Settings (Reset Mobile, Wi-Fi and Bluetooth)
Reboot your device and test the service.
iOS: Tap Settings > General > Reset or Transfer > Reset > Reset Network Settings.
Enter your passcode and wait for the device to restart on its own.
Test the service
⚠️ Warning
Before resetting network settings, make sure you know your Wi-Fi passwords, as you will need to reconnect to them afterward.
Next Steps
If the service is still not working properly after doing these checks and trying these steps then email us with the following information:
- The IMEI of the device:
- The exact location where you're experiencing the issue (full address required):
- Any error messages that appear on your phone:
- Which of the troubleshooting steps were you able to perform? (please specify):
- Please specify which services are affected by this issue (calls, texts, data):
