Text-message spam is becoming a costly nuisance for cellphone customers, as service providers struggle to block the millions of messages sent every day.

The Canadian Wireless Communications Association says wireless spam is more problematic than common email spam because it "follows the customer" and can result  in hundreds, even thousands, of dollars in charges for the handset owner.

As Chalsi Goetz found out, even unlimited incoming-text messaging from a service provider doesn't stop charges from accumulating.

Goetz's son received hundreds of text-messages sent by strangers to his cellphone, prompting his mother to investigate why his monthly charges were so high.

"We had 689 texts at 50 cents each, so he was averaging 22 a day," she told CTV British Columbia.

The charges, for premium message services, totaled $344.50.

Some companies, such as TELUS, offer free spam control to their customers; however, Goetz's spam was listed as "information services" -- a convenient loophole, utilized by spam senders, that allowed the messages to be billed to her account.

Goetz said it was impossible to stop the messages from reaching her son's cellphone.

"They did have 'press stop' at the end of the text, but when my son did that, the next day it would be 'press pause' and the next day it would be 'press receive' or there were different types of stoppage," she said.

Shawn Hall, a spokesperson from TELUS mobility, told CTV News that the company is doing what it can to protect customers.

"It's unethical business practices for sure and we're doing what we can to shut them down," he said.

"The best way that people can protect themselves is to treat their cell number with great care. If you're online and someone is asking for your cell number be very careful about giving it out."

Goetz contends TELUS isn't doing enough and should be providing all of its customers with information to stop text-message spam.

"There is no consumer information from them to protect their customers with regard to this matter and that's what I think is wrong," she said.

TELUS refunded the hundreds of dollars it charged Goetz and provided her son with a new cellphone number.

Until 2002, text messaging was limited to messages between customers on the same network. Now carriers offer inter-carrier text messaging and email messaging on handsets -- the most common form of text-message spam.

Statistics Canada estimates at least two-thirds of Canadian households have cellular service. By the end of 2005, there were 16.6 million subscribers to mobile communications services, the agency reports.

With a report from CTV British Columbia's Chris Olsen