A telecom watchdog group says routine errors on cellphone bills continue to be a major headache for consumers, who often complained they were charged too much.

A report by the Commissioner for Complaints for Telecommunications Services finds consumers also say they weren't given discounts or credits promised or their contracts didn't reflect the services they thought they were getting.

The non-profit group helps settle disputes between consumers and telecom service providers.

It handled almost 11,000 complaints for 2011 to 2012, a 35 per cent increase from the previous year.

The complaints included wireless, local phone and long distance and Internet services.

For the last three years, complaints about cellphone services have made up more than half of the telecom services complaints, a hot button issue for consumers.

"The No. 1 complaint is what I will call routine billing errors related to regular service," said commissioner Howard Maker, who released his annual report Thursday.

"Wireless tends to be a complaint generator," Maker said.