The only way to ensure you’re calling amex is to call the number you know, otherwise the scammer will have you call another one.
"Hey, we need to talk about your account. Call our general enquiries number on our website, press 9 and enter 'XXXXXX' to be reconnected to me."
Edit: perhaps the extension would be per transaction, not per-agent, and when the customer calls the extension, the agents system can automatically pull up the customer’s account. These extensions should expire, but given the length of some customer calls, and how often I’ve been disconnected from customer service lately, perhaps it should be on the order of hours, not minutes or seconds
Email is pennies per thousands.
Phone calls are cheap especially for nonconnected or robocalls (which would cost for a postal contact).
Postal mail costs $0.50 US in postage alone. The full-up cost of a mail campaign is often several dollars per mailed item, though in bulk, and with bulk rate, I believe it's closer to $0.40 (postage plus a few cents for paper and envelope).
That would cover many thousands of email contacts, possibly nearly as many phone/VOIP attempts.
And the systems required to successfully and accurately generate a postal response on request are also high.
Low-cost systems are high-fraud systems.
I was disappointed that no alert was sent through the banking app. That would be the most secure option but is explicitly disallowed in the notification settings.
They can include information in the letter they can't include on a phone call, as the mail service is performing the authentication.
My health insurer won't talk to me on the phone without me confirming identity, even if they called me, but they'll happily mail the info.
Never call the number off the letter, though.
Eventually they did suggest I call the number on the back of my card, but I was annoyed by their lack of professionalism by this point (I mean, they are asking me to do stuff - giving out information to unknown callers - which they themselves always tell customers never to do!) I said I wasn't going to phone a general number and get stuck on hold for hours over an unknown issue - either give me some reference to get through quickly to the right person, tell me what the problem is now, or send me a letter. But they kept claiming that they couldn't send out letters in the post :-(
In the end, I finally received a letter by mail telling me that there were problems with my direct debit payments. So it was a genuine call but their inability to securely make these calls is frustrating.