Can you use thr new nokia lumia 640 and 640 XL with walmart family mobile?

Hey me and my sister wanna upgrade to the Nokia Lumia 640 but we have WalMart family mobile as a contract and we want to know can you use it with WalMart family mobile and ideas or help? Please thank you and right now we have the Nokia lumia 530

Read more: Can you use thr new nokia lumia 640 and 640 XL with walmart family mobile?