Business credit cards with solid customer support?

I have had an Amex personal card for ~30 years and had a business gold card for about a decade. Almost no problems with the card or getting charges reversed until December 2008. In between all of the financial industry nonsense that fall, one of my clients failed, which caused me to miss a single payment to Amex in November 2008. I was able to cover that payment in early December as well as the December payment. On a cold December night in Chicago, I was standing at the O'Hare rental car counters where I learned that Amex had frozen both my personal and business cards over the missed November payment, even though the business card was allegedly separate from my personal account, and I had made both the make up payment as well as the December payment.

They only restored my personal card once the entire outstanding balance on the business card was paid off (I'd carry a balance on the business card but routinely paid off the personal card).

I still have the personal card but use it sparingly (it has a very high limit that I am unlikely to get on a new card due to extreme fluctuations in my annual income). I closed the business card a few months later (ironically, to move to Capital One).

My advice: either don't run a balance or only carry as much as you can afford to pay off if necessary. If you can get Amex to treat your company as the guarantor you might avoid the personal tie–up I got sucked into (my business was too new when I got the business card so they required my personal guaranty. Oops.).