Switch to four new qualifying T-Mobile lines from a qualifying provider, and trade in four eligible devices, and you can get four iPhone 15 smartphones for $25 per line ($100 total). The credit will be applied via 24 monthly bill credits. $35 line activation fees will apply. If you cancel your plan before the 24 credits are applied, the credits stop, and the balance may be due. It costs $5 more per line without Autopay.