Can I keep the phone numbers I purchase?

In this article:

Under the FCC's local number portability (LNP) rules, you are legally able to keep your phone number when you move or change phone service providers. Any number purchased for use with our service is yours to take with you. 

You will need to fully port the number away to your new service provider before canceling your service. Finally, it's always wise to check in with your desired carrier or service provider to ensure that they can support your number.