Use a SM-N9005 on AT&T? topic

I have a sm-n9005 and I'm trying to use it on at&t. I bought the sim card and literally just got the prepaid plan. my data isn't working though. The at&t guy said my phone is blocking the data. I can make and receive calls. I think he was trying to get me out the store. Can someone help me on getting data working?

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