Omnicom Group, Inc_ phone with blue background by- rafapress via Shutterstock New York-based Omnicom Group Inc. (OMC) offers advertising, marketing, and corporate communications services. With a market cap of $15 billion, the company’s agencies, which operate in major markets around the world, provide a comprehensive range of services, including traditional media advertising, customer relationship management (CRM), public relations, and specialty communications. The global leader in marketing communicatio ...