Will att notice if swap sims?

I HAVE AN IPHONE 4S AND I'm GETTING THE IPHONE 5S I KNOW THAT THE IPHONE 5S HAS A SMALLER SIM. I HAVE SIM ADAPTER I JYST WANT TO KNOW IF ATT WILL NOTICE WHEN I SWAP SIM?

Uhm.well if it has a smaller Sim slot, then I doubt you can put the old one in the 5s. And if you're setting up a new plan, then yeah it could work with a new Sim card but if you're planning on getting a new phone and it's not on your plan, then the phone won't be active and won't be able to text or make calls.

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