AMEX & Curve Curve has been forced to drop Amex from its list of supported payment cards that can integrate into its own prepaid card and connected mobile app. Curve told the publication that it has offered a full refund to all of its customers because of the sudden change. Reports said one of Curve’s biggest selling points for its small business and entrepreneur users was that its clients could make purchases on the MasterCard -branded tool using their American Express cards loaded on the solution. That meant merchants that weren’t accepting American Express cards at their POS could accept the MasterCard Curve card, while payers could rack up rewards like air miles via their American Express card programs. Curve also reportedly allowed users to gain rewards points when they withdrew money from an ATM via their American Express card using the Curve card. According to the company, it lost money when purchases were made using an American Express card because it would be