Could you give us a little more information about the issue that you are having? I tested this quickly and it seemed to work fine.
I turned on point selection like so:
lineSeries.selectionMode = SChartSelectionPoint;
Then I set up my line series so that the points would become unselected when they were tapped:
lineSeries.style.pointStyle.showPoints = NO;
lineSeries.selectedStyle.pointStyle.showPoints = YES;
When I tapped a point, the point disappeared as specified by the selectedStyle object.