Who is this calling? Apparently American Express. Why is the number listed as a cellular line?
I listened to their message which requested a call back 1-800-678-0738 about an urgent matter which required my attention by the end of the day. Sounds incredibly fishy:
This is American Express calling about a very important business matter. Your attention to this matter is urgently needed by the end of the day. Please call us at 1-800-678-0738, and please have your American Express account available when you call. We can be reached 24 hours a day, thank you.
I don't think so, you'll have to do better than that. If this is actually American Express, it reminds me of how unprofessional I found the PayPal / GE Money Credit Card phone representatives to be when I spoke with them.
There appear to be various reports on the web about whether or not this number is actually American Express or not. Either way, I played it safe and called the number on the back of my card. I spoke with a representative and inquired about the phone call and he said there was no indication on any of my accounts as to why they would have been calling.
So, whether or not the caller was actually American Express or not, the matter was not urgent. If it were, I imagine that the representative I spoke with at their official number would know what the matter was.