The end might be near for Unlimited Data with T-Mobile USA. What today's newest plan does is introduce a $100 two-person plan that gives each person 10GB of data on 4G LTE. Each additional line after the first two is $20 per month, and each additional line added gives that person 10GB of data. You can also add an additional 20GB of data to a person's plan for $10. Once your data per month is used up, your speed decreases - the plus side is you still have "unlimited data" to use.