I received a call and transcription of the message through Google Voice. It's pretty clear that this is not Amex. We are not cardholders and the message is semi-literate.

Don't Call! This is a scam number/phishing scheme. They say they are American Express, but they are using a voice-modulator to disguise the robo voice. They will try to get your password. They also use 800-528-4800. They are probably using a serivce like www.spoofcard.com to fake their caller id. It's easily done.

Call today but left no message.  Caller ID says "800 Service".  Others mentioned American Express.  I have been getting a lot of Amex calls with many different caller ID numbers.  Sometimes they would leave a recorded messages saying something like "This is American Express and this is not a telemarketing call ..." and asked you to call back on another toll free number.  I am pretty sure it is a scam and they are not from American Express.

AmEx Account Services no message

multiple call to cell phone

888-395-4133 = American Express   If you're a day late you'll get multiple calls from various toll free numbers... their way of skirting harrassment laws apparently.

Any idea who could call from this phone number.

It's AMERICAN EXPRESS COLLECTIONS. Called the number back and got an AMEX operator within 5 seconds.

Number called my cell phone on a SUNDAY! Hung up when I answered.

This number called my cell phone at 8:00 AM Saturday.
Caller ID appears to be set at 888-395-4133 as well.
No message