How do i contact gsi customer service? Please feel free to call us anytime at 877.GSI.1956 or click the “Contact us” button below to send us an email or visit our office. We look to take care of issues before they become problems.What services does gsi provide? GSI currently services 100 + Consumer Energy facilities throughout the state of Michigan. GSI also provides design/build services for all new construction, as well as any additions and changes to their existing security systems.How do i contact the gs1 office? United States Phone: + 1 937 435 3870 Website: www.gs1us.org Email: [email protected] What is gcis customer service phone number? Customer Service is a top priority at GCI. We want to hear about your experiences good and not-so-good. If you have feedback about service, billing or customer service, we would love to hear from you! 800-800-4800.