How can I request a Domestic SIM unlock to use my Boost Mobile phone on another carrier?
Boost Customer Care can help with this request, however there are some requirements that must be met before the device can be unlocked. You can also view this information on the Boost Mobile support pages
Boost Mobile also has a pretty thorough set of Unlocking FAQs on the support pages, as well.
Keep in mind, once you have unlocked your device and activated it on another carrier, you may not be able to reactivate it on Boost Mobile.