For BMO Mosaic Mastercard Support, here are the numbers to call for help, as from the back of a BMO Mosaic US Dollar Mastercard, which seems to be the only no-fee US$ card in Canada:

USA/Canada: 1-800-263-2263

Overseas (Which you may call collect): 514-877-0330

Here are all of the public Bank of Montreal TelePhone Numbers:

General Inquiries English: 1 877 CALL BMO (225-5266)

Overseas (ie: outside of Canada or US): (416) 286-9992

Direct Banking TelePhone Number: 1 800 363-9992

Direct Business Banking Telephone Number:  1 877 345-7777

BMO Credit Card Customer Service Telephone Number: 1 800 263-2263

Bank of Montreal Mutual Funds: 1 800 665-7700

BMO InvestorLine:  1 888 776-6886