Problems with iMessage after iPhone update? Check the SIM, says Apple

Have you found yourself unable to send or receive messages on your iPhone? Or are iMessages being sent from your email ...
The Droid Guy

iPhone 15 No SIM card detected? Here’s How to Fix It!

The iPhone 15 relies on your carrier’s SIM card to connect to cellular networks. A “No SIM Card Detected” error indicates a disruption in this essential process ...

7 ways to troubleshoot if your phone's SIM card isn't working

If you can't make a call or if you see an error message that your phone's SIM card is not working, there are several ways to ...

How to remove the SIM card from your iPhone to replace it or throw it away

To remove the SIM card from your iPhone, you'll need to eject the SIM card tray with a special tool or paperclip.
CNET

New iPhone? How to Activate a New SIM Card in 5 Easy Steps

Sareena was a senior editor for CNET covering the mobile beat, including device reviews. She is a seasoned multimedia journalist with more than a decade's worth of experience producing stories for ...
Ars Technica

SIM card and signal strength

Cellular reception of my mobile phone company's network has always been weak (on 3G; forget about 4G) in the house we moved into 2y ago but the past 48 hours I'm barely getting beyond the "No Signal" ...