We’ve heard numerous stories over the years of Americans who unwittingly or inadvertently tallied up huge voice and data bills while roaming internationally in Canada or Mexico, and wireless providers have been perfectly happy with the substantial fees they earn each year off callers traveling north and south of the border. Today, T-Mobile announced that, starting next week, all its Simple Choice plans will cover calls and data usage in many areas in Canada and Mexico.

Dubbed “Mobile Without Borders,” T-Mobile says that beginning on July 15, Simple Choice subscribers will have access to 4G LTE data at no additional charge in Toronto, Montreal, Vancouver, Cancún, Acapulco, and dozens of other cities (see full list here).

Additionally, calls from T-Mobile customers to any number (landline or wireless) in Canada or Mexico will be covered as part of existing plans at no additional charge. The company says that other benefits — like its “Music Freedom” program that doesn’t count certain music streaming services against your monthly data usage, and WiFi calling and texting — will likewise be included all over North America.

BUT… before you run off to Mississauga to try out this feature, current T-Mobile customers will need to opt-in to the program, either by calling T-Mo customer service, going to a T-Mobile store, or online at my.t-mobile.com.

T-Mobile says Mobile Without Borders is available at no charge to all prepaid and postpaid Simple Choice users. Business plan-holders won’t face any additional fees for their first 10 lines opted-in to the program, but will pay $1/month for each additional line included.

In the last year, AT&T has looked to expand its network into Mexico with the purchase of two providers, Iusacell, and Nextel Mexico. So of course, T-Mo’s puckish CEO John Legere took this opportunity to poke fun at his bigger rival.

“After spending billions buying up Mexican telecoms, AT&T’s CEO is promising ‘the first seamless network covering Mexico and the U.S.,’ something ‘unique’ that ‘nobody else will be able to do for the consumer.’ So much for that. They won’t be the first. And they won’t offer Canada for free,” said Legerre. “We’ve done this the Un-carrier way − reaching across borders, partnering with leading providers offering the best LTE networks, creating a simple solution right now − then not charging a penny more for it.”

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