Bell's internet usage tracker may overstate the amount of bandwidth its customers use, the company acknowledged this week on the website where people log in to view their usage data.

Most customers have usage limits that determine how much they are billed.

Bell has "identified an issue that may cause internet usage shown on this site to be overstated in some cases," the company said in a message posted to the website.

"In order to ensure we provide reliable information to all our clients, the usage tracker will be unavailable while we resolve the issue. We apologize for the inconvenience."

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The problem affects fewer than 0.1 per cent of users and has been traced to software supplied by an external vendor, Bell told CBC News in an email.

The company added that the vendor has provided a fix, and Bell expects the site to be back online "certainly before the end of the week."

In the meantime, it has removed all usage charges for those affected.

Bell and other large internet service providers charge customers based on the maximum amount of bandwidth they are allowed to use each month as they perform activities such as streaming movies and music, talking over Skype, playing online games and downloading and uploading files.

Customers can choose different price plans based on the size of their usage caps. Bell says this ensures all users pay their fair share, and light internet users aren't unfairly subsidizing heavy users.

Overage charges up to $2.50 a GB

If users go over their bandwidth cap, they face "overage" charges of up to $2.50 per gigabyte.

Canada's internet regulator, the CRTC, announced Tuesday that it is reviewing its decision that would effectively force many smaller ISPs to charge customers based on the same usage caps.

Many of those smaller ISPs rent network access from Bell to create retail internet packages for their own customers.

The CRTC's ruling that Bell could charge those ISPs — its wholesale customers — based on the same usage-based caps it charges its retail customers would mean those ISPs would have to lower their usage caps and would no longer be able to offer unlimited internet access.

The issue caused a huge public outcry, prompting Industry Minister Tony Clement to warn the CRTC he would overturn its decision if it did not do so voluntarily.

Data tracker gives different numbers

Jerry Shulak of Côte Saint-Luc, Que., says he contacted Bell after noticing a few weeks ago that his data usage "seemed to be inflated over what I was actually using."

Shulak called Bell customer service and was told the tracker was "100 per cent accurate," he said in an email to CBC News.

Shulak, who was skeptical, installed his own data usage tracker and found that over two weeks, Bell's numbers were consistently 50 to 200 per cent higher. He noted that he has only one computer in his home and no wireless access.

Michael Geist, a University of Ottawa law professor who holds a Canada research chair in internet and e-commerce law, said in a blog post Wednesday that he believes the federal commissioner for complaints for telecommunications services may need to get involved in the issue.