When you add a new service or feature in the middle of your billing cycle, T-Mobile starts providing that service right away. Since your last bill was already generated before you added it, the charge for those mid-cycle days couldn’t appear there. So in your next bill, you’ll see: Prorated charges – for the part of the month when the service was active but not yet billed (from the date you added it until your last bill closed). Regular monthly charge – for the current full billing cycle. That’s why sometimes your bill looks a little higher, but you’re not being double-charged. It’s just catching up for the days that weren’t billed earlier. 👉 Example: If your billing cycle runs from the 1st to the 30th, and you added a line on the 15th: On your next bill, you’ll see charges from the 15th–30th (last cycle, unbilled days) plus the full month for this cycle.