Will an unlocked iPhone originally from Sprint work on an AT&T go phone plan?

I found one on eBay, and I'm gonna join the $25 AT&T go phone plan. It's an unlocked iPhone 5c, and it says its originally from sprint, but will work on any gsm network, which AT&T is. But will it work? Or would I be wasting $300?

You would be wasting $300. The Sprint version can't be unlocked for use on other US carriers