Earlier today, T-Mobile announced that subscribers to its Simple Choice wireless plans would soon be able to make calls to/from, and access 4G LTE data in, Mexico and Canada at no extra charge (though you do have to take the step of opting in to the new plan). But what about those T-Mo users who have been holding on to their pre-“Un-carrier” plans? If they want access to this call-anyone-in-North-America option, they’ll have to ditch their old plan or pay up.

After hearing about some social media grumblings from grandfathered T-Mo customers who weren’t sure whether they could finally make free calls to that girlfriend/boyfriend they met at Niagara Falls back in 7th grade (you wouldn’t know them), we checked with T-Mobile HQ, which clarified a few things:

1.Here are the plans eligible for the free upgrade
• All “Simple Choice” plans for consumers and businesses are eligible (though businesses will have to pay $1/line for every phone after the first ten);

• Mobile Internet plans with 1 GB to 21 GB;

• “Match Your Data” Mobile Internet plans, tablet data for life plans;

• T-Mobile Prepaid (but not “Simply Prepaid”) plans.

2. Adding Mobile Without Borders to grandfathered plans will cost you

If you’ve got a grandfathered, or “legacy,” plan that pre-dates T-Mobile’s switch to the Simple Choice model, you can access Mobile Without Borders, but at an additional rate of $10/month. The other option is to switch to a Simple Choice plan.

3. Even Simple Choice users do indeed have to actively opt-in to Mobile Without Borders

We’ve heard from some readers who called T-Mobile today and were told by reps that they didn’t have to opt-in to MWB, that it’s going to be automatic. The corporate media rep we contacted confirmed that customers must actively make the choice to join the program. All Simple Choice customers are eligible but that doesn’t mean they will be switched over. Note that the new plan doesn’t kick in until July 15, so the website might not be updated with the opt-in yet, and phone customer reps might not yet be fully informed on the topic.

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