That's not necessarily true at all. To begin with, there are winners and losers on each end of natural selection. While charity may not help an individual it has every possibility of helping the wider species.
Natural selection also only really matters in that you get the chance to breed. Whatever you do before or after that is irrelevant if you get that opportunity. Charity also doesn't mean you bankrupt yourself or diminish your own resources to the point you can't survive. (Some take it to extremes however of course). It often has little or nothing to do with your chance at breeding and survival unless you do take it to extremes.