If you filed an AR-11, then you notified them correctly. I would still call the 1-800 customer service number and let them know that you are waiting for a interview to be scheduled in North Carolina. Be proactive!
You need to call and take this up with the USCIS nationwide 800-number service. Will not be easy or fast. You'll have to constantly follow up with them.
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It sounds as though you did everything right. What you may want to do is schedule an InfoPass appointment with the USCIS nearest to you and just make sure that your file is being transferred to North Carolina. The transferring of cases can take a long time, so waiting a few months isn't out of the ordinary. Also, if you didn't do it at the time, make sure you do an AR-11 change of address online.
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