For 24/7 help with technical support, account changes, and supply orders, call 1-888-263-1938. If you need product-specific support in the U.S., Fiserv also lists dedicated lines such as Global Gateway (+1 888-477-3611), Global Leasing (+1 877-257-2094), and Payment Software (+1 800-365-1998), plus financial-institution support like Card Issuing/Signature Debit/Health Care (+1 800-337-1222), Debit Card & ATM Help Desk (+1 877-866-7827), and Instant Cash for existing clients (+1 800-641-0035).