Apple 4s, plug in a mobile phone card, can't make phone calls and send text messages, showing no service. What happened?

If there is no signal on the mobile phone or there is no service or emergency call displayed on the screen, it is suggested that:

1. Try searching the network again after shutdown and restart.

2. If it is a dual-card mobile phone, please check whether the SIM card is activated: Settings -SIM Card Manager -SIM 1/SIM2- Click the SIM card icon-Slide to open (the operation of different models of mobile phones may be slightly different).

3. If there is still no signal, it is recommended to turn off the mobile phone, take out the SIM card, clean the SIM card chip with an eraser and reinstall it.

4. If it doesn't work, please try to change to another location to rule out whether it is caused by poor signal coverage at this location.

5. Try to change the network mode to 3G or 2G (automatic connection mode is not selected). Note: Some machines do not support changing the network mode.

6. Try to replace another SIM card.

7. Update the mobile phone system version: Settings-About the mobile phone (about the device)-Download the update manually/automatically (software update/system update-update). Note: Please back up data (contacts, information, pictures, etc. ) in the device.

If there is still no signal or emergency call after the above operation, please bring the purchase invoice, maintenance card and machine to the service center for inspection.