[Sgt_Tropo]

Pardon my ignorance, but I, and am sure there are many others, who am under the impression that automatic / electronic withdrawls can not be made by any entity (other than the IRS) for any debt without your signed permission, or a court order. I also have the understanding (passed upon talks with a lawyer friend of mine) that if Amex or any other entity makes an unauthorized withdrawl from your checking / savings account for any reason without your expressed and signed permission, they stand to lose a great deal of money in fines and forfeitures, as well as possible prison time.
Are you absolutely sure that no one in your business signed an agreement ? Is this occuring on a Corporate or Business AMEX card and not your personal card ? If so, you or the business probably received a notice of the change in policy from AMEX, which most likely said something to the effect that, "continued use of the card(s) after a specified date constitutes an agreement to the new policy".
I get these types of statements all the time on various charge cards and accounts payable. When I do not agree to them, I simply stop using the card / account, or send them a written objection and denial of approval for the new policy. The company then is required to respond in writing to either accept my objection or terminate the account. Of course, account termination for this reason cannot result in an acceleration of payments, whereas non-payment or not meeting the stated minimum payment CAN result in the entire debt becoming due and payable immediately. By the way, the courts have upheld this acceleration of payment in the event of non-payment or not making the minimum payments previously agreed to by both parties.
I do not agree with such a change in policy without requiring some kind of signed and dated acknowledgement, but then there are lots of things I don't agree with.
Just wanted to let you know what might have happened to cause this to happen. You might ask AMEX to send you a copy of the policy change notice and see if it "jogs" any memories.

Be careful out there. It's a cruel, cruel world.