Can i use my SIM card on an iPhone 4s?

My recent phone broke it was a go phone from AT&T and i still have about 7 months left on my 2 year contract. I was wondering if i could take the sim card out and get it resized to a micro sim card and put it in an iPhone 4S from AT&T and use it as my phone with the same number / plan and stuff. Is that possible?

I'm pretty sure that will work fine. Call ATT customer service to be sure.