I would suggest contacting the Chairman's Office.

I had a payment declined by my bank once (bank error). AMEX went out of their way to help me. I'm surprised they would come down so hard on you, especially with your history and charging activity.

Maybe there is something else going on? Have you looked at your credit report recently?

Given your level of spend, I'm sure you wouldn't have a problem opening an account at UBS, JP Morgan or a similar private bank. You can typically get credit card limits well north of $100K at those institutions if you are a private banking client.

In the same vain, you should also be able to use a debit card linked to a brokerage account and draw off the available margin balance (sky is the limit here assuming sufficient collateral and having your financial advisor remove daily spending limits from your account).

Otherwise, I don't know of many other issuers that will offer such high credit limits. I'm sure someone will chime in with other options.