I was suspicious of the noise in the background, just didn't seem right. But I did apply for Amex card 10 days ago and they knew all of the information about it. I told them I'd call back but if it is a scam AMEX has some real security issues.

They wanted to call my bank to verify my address, so that seemed rather fishy, never heard of that before.

This call is a fraud. I didn't pick up and they left a voice mail saying that there is a questions regarding my name. I was suspicious so called American Express and said that they never called me and there was no problem with my account. DO NOT PICK UP THIS NUMBER.

I sent this e-mail to American Express:
"I got a call from 801-945-5000, caller ID said "American Exp", they asked me to call back at 866-379-3643, are these numbers really AmEx? When I called back, they asked for my social security number, when I refused, the representative hung up on me? Is this a rip off phone number? Why else would they hang up?

Here is the answer from American Express:

Thank you for writing in.

The number from which you received a call as well as the call back number left with you, do not belong to American Express. It was a Phishing call.

Please be aware of such calls and do not give out any of your sensitive information.

Have an excellent day!

Sincerely,

Barkha Rastogi
Email Servicing Team
American Express Interactive Services
============================
I suspect that all of the comments above saying that the number is OKAY & really American Express are part of the Phishing scam and are bogus testimonials trying to counteract the alert process from 800notes.com.
============

I got the phone call from this number and the lady told me she is from Amex fraud prevention center and she likes to talk to me about my account with Amex.  And she asked me personal questions to check my identity.  I didn't tell her anything but told her I will call Amex directly.  She told me her name and another phone number to call back (1-800-446-6307),

I went on the Amex website and called the customer service number (1-800-528-4800) and the guy told me he wasn't sure if the 1-800-446-6307 is legitimate but he can call and connect me to that number directly.  So he did and I was connected to the Amex banking.  The lady at Amex banking said she can't tell there's anything wrong with my account.  But she said it sounds like it might be someone from credit card fraud department so she put me on hold and tried to find the first lady who called me.

She did and it turned out that I provided one address when I first open my account and provided a different address when I opened another account a few days ago.  So they were wondering if there's a fraud going on.  So, from my experience this number is legitimate.

Fun fact - I just called AmEx to inquire about this number, and although it IS a legitimate AmEx number, the representative also said that they would never call to verify customer information.  If there's a problem with an application, they will e-mail the applicant or mail a letter, asking them to call an 800 number so that they can verify the missing information.

So although the number is legitimate, anyone calling to ask about personal information certainly is not.