Last updated on June 27th, 2019 at 03:39 amBMO Harris Bank Customer Service Phone Numbers Customer service: 00 1 847-238-2265, 1-888-340-2265 BMO Harris Bank Credit card support: 1-855-825-9237, 1-262-780-8658 (outside U.S.) Small Business Online Banking Support: 1-888-340-2265 (24 hours a day) Online Banking: 1-888-340-2265 New Products & Services:1-888-340-2265 (24 hours a day) Apply for a credit card: 1-888-340-2265