If you have a Boost Mobile phone, consider switching to Sprint and keep your current smartphone.
If your Boost Mobile phone has been unlocked, Boost customers have the option to switch to Sprint and bring their existing phone.
The reason for this being possible is because Boost Mobile runs off of the Sprint network and is supported by Sprint towers. This means any unlocked Boost device that is paid off and has a clean ESN is eligible to switch to Sprint.
Once your phone is unlocked, simply purchase a Sprint SIM card and a Sprint service plan. Once you've made your purchase with Sprint, insert your new SIM card and enjoy.