Yeah I wanted to address this in my comment above but didn't want to get down in the weeds. There's a couple decent solutions to this problem. The liberal/socialist approach would be to make a contract garnishing future basic income illegal. The libertarian approach would be to make bankrupcy laws so frictionless that you could declare bankrupcy three times a week without breaking a sweat, causing payday loan companies to stop offering their services to the least financially responsible sector of the population.

I think either of these solutions could be made to work in general. Certainly better than what we have right now.