This is a phishing scam. Got a call and VM this morning from this number. The voicemail did a good job of making it sound like a legitimate call from American Express, with a reference number and extension. I called the actual American Express and they confirmed that this is not one of their numbers. Do not give any information to this number.
It is American Express. They were following up on a customer service issue I reported earlier in the day. It was actually the same person I spoke to when I called the main 800 number on the back of my card. It is their Utah office and was a legit call.
But there would be a reason for American Express to call you.......if someone applied for their card IN YOUR NAME. So, don't blindly assume that they would only call you if you had applied.......calling is how they catch fraudulent applicants using someone else's name.