Misleading wireless and internet contracts have become the most common issues brought to Canada's telecom complaints watchdog.

A significant part of that was a surge of complaints that small carrier Wind Mobile had violated Canada's Wireless Code of Conduct after it suspended customers from its unlimited U.S. roaming package because of what it called "excessive usage."

The latest annual report from Canada's Commissioner for Complaints for Telecommunications Services shows that, overall, the number of complaints has fallen 12 per cent, to 9,988.

In general, the top type of complaint was about misleading or missing information in customer contracts — the watchdog received 2,475 of those.

"That's a bit unfortunate and we're a little bit surprised to see this," commissioner Howard Maker told CBC News in an interview. He added that his agency had hoped that the Wireless Code of Conduct, introduced to protect customers in late 2013, would help ensure customers get better information and reduce the proportion of complaints about lack of disclosure.

Last year, the top complaint was about billing.

Maker added that there has been an increase in complaints about issues of non-disclosure not just for wireless contracts, "but across all lines of business." And that's a concern because telecom customers are typically locked into the terms and conditions of contracts for a set amount of time — up to two years.

A major complaint was from customers who said their service provider had changed something significant in their contract without providing notice. The commission said it saw a 72 per cent increase in this type of complaint for wireless services and more than 400 per cent for internet services.

The complaints watchdog said it was also concerned about an increase in complaints about internet service, which made up 26.1 per cent of the complaints this year, up from 20 per cent last year.

Wireless code breaches

Meanwhile, for the first time, complaints about wireless service have declined — down eight per cent to the current 52 per cent of all issues.

But among those complaints, the number of violations of Canada's Wireless Code jumped from 30 last year to over 500 this year.

Maker said most of those were from 80 customers who complained about Wind's unlimited U.S. roaming plan.

"Telecom is the only place where you can sell someone an unlimited service that's actually limited," he added.

While that's allowed, carriers need to disclose the limits in their "fair use policy" — something Wind didn't do. In fact, its limits varied on a month-to-month basis, which isn't allowed. "So customers could not even phone up and ask 'How much usage am I allowed this month?'" Maker said.

Customers whose use exceeded the limit were suddenly disconnected, in violation of the Wireless Code of Conduct.

Complaints about Wind jumped 37.6 per cent to 702 this year, even though the company has only around 800,000 customers.

In a statement explaining its poor record, Wind said 80 per cent of the complaints arose from its imposition of a cap on its unlimited U.S. roaming plan in July 2014.

"This became necessary because of extreme usage by a small number of customers on this plan," Wind said in its statement.

It claimed fewer than 50 customers were involved, but the commission received multiple complaints from each customer, the wireless carrier said.

As usual, Bell and Rogers topped the list of companies that customers complained about. But while the number of complaints about Bell have held relatively steady at 3,599 and those about Rogers have dropped 23.7 per cent to 1,814. Bell has more than eight million subscribers and Rogers more than nine million.

Deepak Khandewal, chief customer officer for Rogers, said the company is pleased with the results. He said making contracts, bills and communications with customers simpler and clearer has led to a decline in complaints.