How will unbanked get access to Libra?

1.7b Unbanked is a number that gets thrown around in the Libra PR quite a lot. However, given Libra will be obtained by exchanging existing currencies, how does FB plan to ensure unbanked in remote corners of the world have access to Libra?

I was thinking there would be some way for the unbanked to earn Libra on FB. Thus they would immediately be banked.