Sprint/ cdma phones how easy is it to switch phone back and forth?

[Perry the Platypus]

Sprint/ cdma phones how easy is it to switch phone back and forth?
ok so i had at&t before with iphone and when i went hiking i switched out the sim card to a less expensive phone so it wouldnt break


now i know sprint doesnt have sim cards so i am asking how can i switch my service from one sprint phone to another