How To Write A Letter To American Express Corporate . Initial complaints should be directed to american express directly. You can find contact details for american express above. 9+ Complaint Letters Free Sample, Example, Format Free & Premium from www.template.net Corporate details (cont.) aex9559 10/15 Request you, until further notice in writing, to debit our account detailed on this form, any amounts which. The american express company, also known as amex, is an american multinational financial services corporation headquartered in manhattan’s three world financial center in new york city.