I am having activation error problem with my iPhone 5s. I did research on net but did not find anything. Can you help me?

Okay, so did you try connecting to the computer and iTunes? If not, then try that. If that still does not work, then you need to contact Apple Support using the link provided. This is a user to user support forum and Apple does not participate here.

Also, make sure that you have the latest version of iTunes installed on the computer and you have a stable internet connection.

If you would provide the error number, it might help. When you see an error screen, please provide the exact text of the error for assistance.