Bank of Montreal Customer Service Phone Numbers Bank of Montreal Customer Service: 1-877-225-5266 Customer Service: 1 800 363-9992 Lost or Stolen Card: 1-877-225-5266 BMO Mastercard: 1-800-263-2263   Bank of Montreal Headquarters Info, Email, Phone number, Website and live chat Information The Bank of Montreal is a Canadian multinational banking and financial services corporation. One of the Big