Per an internal document viewed by the outlet, the promotion is called “Stay Magenta,” and can only be offered and activated by customer care representatives. This means you can’t activate it on your own. Even in-store representatives won’t be able to help with it.
Your only hope of receiving this offer is through a customer care agent either on the phone or through social media.
The last time T-Mobile offered a discount like this was in March when the carrier offered a discount of $10 for 6 months to boost customer retention.
If you are on the fence about ditching T-Mobile, you might want to reach out to a customer care representative and see if a discount will change your mind.