To change page indicator dot in iPhone pagecontrol follow the below steps and set of codes.

1. Open The Xcode and Create a new project Name it as MyPageControl
2. select the project and right click and add new files and select a cocoatouch File and inherit with it pageControl name it as MyCustomPageControl.
3. add a UIPageCotrol on mainStroryBoard and a UIScrollView. chage UIPageCotrol class to MyCustomPageControl. Also map them to appropriate Outlet(Pagecontroller with pageControl and UIScrollView With pageControl) And when creating the outlet for pagecontrol in ViewController.h , also import the file MyCustomPageControl like:

ViewController.h:

#importMyCustomPageControl.h

{
__weakIBOutlet myCustomPageControl *pageControl;
__weak IBOutlet UIScrollView *scrollView;
}
NSArray *pageImages;


File MyCustomPageControl is like this:

MyCustomPageControl.h file:

#import <UIKit/UIKit.h>

@interface MyCustomPageControl: UIPageControl
{
    UIImage* activeImage;
    UIImage* inactiveImage;
}
@end


MyCustomPageContorl .m file is Like This:
#import "myCustomPageControl.h"
@implementation myCustomPageControl

-(id) initWithCoder:(NSCoder *)aDecoder
{
    NSLog(@"Initializing the mycustom");

    self = [super initWithCoder:aDecoder];

    activeImage = [UIImage imageNamed:@"selectedImage"] ;
    inactiveImage = [UIImage imageNamed:@"unselectedImage"];

    return self;
}



-(void) dotsUpdate
{

    NSLog(@"self.subviews=%@",self.subviews);
    for (int i = 0; i < [self.subviews count]; i++)
    {
UIImageView *dotImageView = [self imageViewForSubview:[self.subviews objectAtIndex:i]];
        if (i == self.currentPage)
        {  
[dotImageView setFrame:CGRectMake(0.0,0.0, 10.0, 10.0)];// size for the selected dot
            dotImageView.image = activeImage;
        }
        else
        {
            [dotImageView setFrame:CGRectMake(0.0, 0.0, 10, 10)]; //size for the unselected dot
            dotImageView.image = inactiveImage;
        }
    }
}

- (UIImageView *) imageViewForSubview: (UIView *) view
{
    UIImageView *dot = nil;
    if ([view isKindOfClass: [UIView class]])
    {
        for (UIView *subview in view.subviews)
        {
            //[subview setBackgroundColor:[UIColor blackColor]];
            if ([subview isKindOfClass:[UIImageView class]])
            {
                dot = (UIImageView *)subview;
                break;
            }
        }

        if (dot == nil)
        {
            dot = [[UIImageView alloc] initWithFrame:CGRectMake(0.0f, 0.0f,view.frame.size.width, view.frame.size.height)];
            [view addSubview:dot];
        }
    }
    else
    {
        dot = (UIImageView *) view;
    }

    return dot;
}

-(void) setCurrentPage:(NSInteger)page
{
    [super setCurrentPage:page];
    [self dotsUpdate];
}

@end

And ViewController.m File change it to:

#import "ViewController.h"

@interface ViewController()<UIScrollViewDelegate,UIScrollViewAccessibilityDelegate>

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];

    scrollView setPagingEnabled:YES];
   pageImages = @[@"image1",@" image2",@" image3"];

      scrollView.contentSize=CGSizeMake(self.view.frame.size.width*3.0, 0);

    self.scrollView.delegate = self;

    for(int i = 0;i < pageImages.count;i++)
    {

        [scrollView addSubview:[self guideImage:[pageImages objectAtIndex:i] and:scrollView.frame.size.width * i]];
        }

   }

- (UIImageView *)guideImage:(NSString*)imageName and:(int)n
{

    UIImageView *imageView = [[UIImageView alloc]initWithFrame:CGRectMake(x, 0, self.view.frame.size.width, self.view.frame.size.height)];

    [imageView setImage:[UIImage imageNamed:imageName]];
    return imageView;
}
-(void)scrollViewDidScroll:(UIScrollView *)scrollView
{
    int currentpage=self.scrollView.contentOffset.x/self.view.frame.size.width;
    NSLog(@"current page==%d",currentpage);    
    [pageControl setCurrentPage:self.scrollView.contentOffset.x/self.view.frame.size.width];
}

- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView
{
    NSLog(@"scroll");
    [self.pageControl setCurrentPage:self.scrollView.contentOffset.x/self.view.frame.size.width];
}   
@end