How do I add my iphone 4s on at&t?

I just bought a iphone 4s from someone. Would I have to go to at&t to get the phone activated or would they just need to give me a different sim card. I'm not on any kind of 2 year plan with at&t. I'm on a no contract plan

Could I just cut my own sim card and use it on the iphone?

Omid Omidvar2014-02-18T12:53:51Z

Hi,dear.To activate your new phone,for the safty reasons,you have to let them know!?Also at&t has rules and regulations that must be fulfilled!?Good luck+
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