I can't activate my iPhone 4s with my existing apple id,after i erase all the data..

Ok i fully understand, so what will happen to owners like me that are stuck with this problem just got out and buy a new device?

Try recovering your Apple ID/password:

http://www.apple.com/support/appleid/

Another thing that is strange is that its telling my device is linked to my apple id.

but i cannot unlock my device with the apple id, and when i go to icloud to find my iphone my device is not in my device list. How is that ???

I suggest you contact the Apple security team in the link I provided. It could be that they have locked your Apple ID because of suspicious activity. It happens.

Ok thank you very much