That's thanks to the company's Mobile Without Borders perk, which was implemented in 2015.
T-Mobile offered Mobile Without Borders Un-carrier plan which introduced free calling texting and LTE plans for travelers in Mexico, Canada, and US. "Less than 1 percent of people with this benefit travel to Mexico and Canada use over 5GB a month".
Rather than being able to enjoy unlimited 4G LTE while roaming to those countries, customers will now have a limit of 5GB of LTE data. For those on an unlimited high-speed plan, T-Mobile says it's going to send out alerts when you hit 80 percent and 100 percent of your 5GB data limit.
If you really need more than that data, you can still purchase high-speed worldwide LTE data for an additional $25. To stop the users from using "beyond the intent of the product" a capping has been applied to the usage of the monthly 4G LTE data.
Customers will now have a maximum LTE data limit of 5 GB in Mexico and Canada, after which they will be reduced to Simple Global speeds, meaning up to 128 kbps for most plans or 256 kbps with T-Mobile ONE Plus.
When the new cap kicks in, some customers traveling to Canada and Mexico might want to know how they're doing with their data. T-Mobile is known to give the North American customers complete access to LTE beyond their nation's borders.
Additionally, those with topped plans can never again utilize their Data Stash while in Canada or Mexico.It's not surprising that T-Mobile would do this.
If you have any more queries on the change and how it will reflect on your mobile usage, you can check the dedicated T-Mobile FAQ page to get all the answers.