Customers are now able to submit a dispute through their online account. If you need to dispute a transaction related to disrupted travel or event plans, please reach out first to the merchant to understand their cancellation policies – you may get it resolved faster by speaking directly to the merchant.
If you are unable to resolve the matter with the merchant, click here to log on to your account and submit a dispute through the online form. You may also mail your dispute to Card Services, P.O. Box 8802, Wilmington, DE 19899-8802.
Business cardmembers can initiate a dispute by logging on to the website URL listed on the back of your card, by calling us, or mailing your dispute to Business Card Services, Billing Disputes P.O. Box 84030, Columbus, GA 31908-4030.
I personally think it makes more sense for disputes to always be done online as evidence can easily be attached to the original complaint (e.g flight cancellation e-mail).