Can an atheist change? Can an atheist attempt to be a better person, to serve rather than be served without admitting there is a God? Possible I guess, but I don't see why they'd have an incentive. Who would they be wanting to please? What moral foundation are they tethered to? I don't have a clue. There are certainly great people who are atheist, I know a few, but from a general perspective, the goodness from most people is tied to a belief that there is a Creator and that he wants us to love one another. It's what motivates me.
Me without God would be a terrible thing for those around me because I'd be extremely selfish. The good that people see in me (at times), is of God because I so desperately want to please my Father in heaven. More often than not, I fail. But I pick myself up, try to forgive myself as God has forgiven me, and I keep pushing onward and upward. Amen.