The phrase "new and existing customers" refers to both people who have recently started using a product or service, as well as those who have been using it for a while. Full definition
Creating, building and maintaining lasting relationships with new and existing customers by means of telephone calls, conferences, exhibition participation and external training organizing. (jobhero.com)
Provide consulting services for new and existing customers on the utilization of complex brokerage software. (resume-resource.com)
Maintained and documented accurate records of new and existing customers for future business purposes. (job-interview-site.com)