Three Walmart stores in Thunder Bay, Ont., are no longer accepting Visa, the payment company said Monday as it encouraged its customers to take their business elsewhere.

After months of negotiations, Walmart said last month it would eliminate Visa as a payment option at those stores because it believes it pays the retail giant too much in merchant fees. The company has promised to extend the ban on Visa cards to its 400 locations across Canada.

"We have not yet set a timeline for the phased rollout of the change," the retailer said in a statement to CBC News. "We stopped accepting Visa at our three Thunder Bay stores today."

Visa, Canada's largest credit card firm, shot back Monday with a message for Walmart customers.

"Until an agreement can be reached in this commercial dispute, we encourage shoppers to use their cards at the more than 5,200 stores in Thunder Bay that accept Visa," the corporation said in a statement.

Walmart says it pays more than $100 million in fees annually for customers using credit cards like Visa, MasterCard and Discover.

'Fees are too high in Canada'

"The issue is that credit card fees are too high in Canada. We believe Visa's fees should be lower for everyone, whether they are a large retailer, small retailer or a charity," said Alex Roberton, a Walmart Canada spokesman in an email.

"Canadians deserve better than paying a hidden fee that is four-times higher than consumers pay in other countries. We are taking a stand for our customers because high credit-card fees can result in increased prices."

Visa says it offered Walmart one of the lowest rates for any merchant in the country but the retailer wanted more. If it had given in, Visa said, Walmart's merchant fees would have been lower than those charged to local grocery markets, pharmacies, convenience stores, charities and schools.

The Retail Council of Canada has called on the federal government to intervene to mandate lower fees for all merchants.

A spokesman for Finance Minister Bill Morneau says he's waiting to receive a report on a 2014 voluntary 10 per cent fee reduction by Visa and MasterCard before deciding "how we can ensure this market stays competitive in the future."

A recent poll suggested Walmart was winning the public relations battle with Visa, but with a potential cost.

Nearly 60 per cent of respondents to a self-commissioned survey by the Angus Reid Institute said they sided with Walmart, but nearly half of shoppers who used Visa at Walmart in the past year said they would be less likely to shop there if the card was no longer accepted.

Almost two-thirds of respondents to the online poll of 1,527 Canadians conducted earlier this month also said they believe any savings from a cut in Visa fees would mostly line Walmart's pockets rather than being passed onto customers.

The polling industry's professional body, the Marketing Research and Intelligence Association, says online surveys cannot be assigned a margin of error because they do not randomly sample the population.