Security features may be required for some services, such as online banking or shopping. For such connections, you need security certificates, which may be available on your SIM card.
For more information, please contact AT&T.
Important: Even if the use of certificates makes the risks involved in remote connections and software installation considerably smaller, they must be used correctly in order to benefit from increased security. The existence of a certificate does not offer any protection by itself; the certificate manager must contain correct, authentic, or trusted certificates for increased security to be available.
Certificates have a restricted lifetime. If Expired certificate or Certificate not valid yet is shown, even if the certificate should be valid, check that the current date and time in your device are correct.
Before changing any certificate settings, you must make sure that you really trust the owner of the certificate and that the certificate really belongs to the listed owner.
There are three kinds of certificates: server certificates, authority certificates, and user certificates. You may receive these certificates from AT&T.
To view the list of the authority or user certificates downloaded into your phone, select Menu > Settings > Config.> General > Security > Certificate management and from the available options.