South Africa has achieved the feat on 15 occasions:

The prominent and versatile character Hashim Amla has managed to slam four 150-plus totals during his ongoing ODI career. He is followed by AB de Villiers, Herschelle Gibbs and young wicketkeeper-batsman with the trio reaching the feat twice in the day-long format.
Pertinently, Gibbs has slammed 175 which also allowed the Proteas to chase down a record total of 435 in 2006 against Australia.
Also, the Proteas list is graced by Gary Kirsten, Dave Callaghan, and Andrew Hudson after from Jean-Paul Duminy. They went on to cross past the barrier of 150-plus once each.