New and existing customers on a Go5G Plus or Go5G Next plan can trade in an eligible device, and get an iPhone 15, 15 Pro, or 15 Plus for T-Mobile for free (via 24 monthly bill credits). The credits will be split between instant trade-in credits and bill credits. The estimated shipping dates for these phones will vary by size and color – some are as early as September 23, others are a month or more away.