A damaged SIM card in your PDA or cell phone will cause a variety of problems and will negatively affect how your mobile phone works. You may experience everything from error messages to mobile handset failures.
Understand error messages. SIM card error messages are clear indicators of damage or corruption. Some of the common error messages include "Insert SIM," "Phone Locked" and "SIM card rejected or not found."
Be alert to phone-functionality issues. A defective SIM card may cause errors on the device. Some common phone-functionality errors may exhibit the following symptoms or cause the following device issues: poor data functions, cryptic or scrambled picture and text messages (MMS and SMS), a broken voicemail connection, or an inability to save new contacts to the SIM card phonebook.
Determine the damage. To find out if your SIM card is broken or damaged, remove it from the device. (It's typically located under the battery.) Look for physical damage, like warped plastic or fire marks. Test the SIM card again after checking for these physical problems.
Review your options. Hopefully, the above process resolved your issue. If not, you might have to visit the local cellphone store. They will probably perform the same type of test, but at least you know what you're in for. The worst-case scenario is that you will be issued a new SIM card. To protect data loss in case your SIM card becomes damaged, always back up contacts and other information to the device, instead of saving everything directly to that fragile little SIM card.