Heather Knight hit an unbeaten 67 as England beat South Africa by five wickets at the Wanderers to complete a 2-1 one-day international series win.
Anya Shrubsole took 3-35 as England restricted the Proteas to 196-9 from their 50 overs in Johannesburg.
Knight and Georgia Elwiss (61) put on 97 for the fifth wicket in the run chase to set up England's victory.
Despite the win, England stay fifth in the ICC Women's Championship standings, behind South Africa on net run rate.
Only the top four nations qualify automatically for the World Cup, which takes place in England in 2017.
England are currently second in the ICC's team rankings, but were fifth in the Championship table following last year's defeats by New Zealand and Australia.
They won the first ODI in Benoni by seven wickets, but South Africa took the second ODI, their first victory over England since 2004, at Centurion to level the series.