Fit text in UILabel

Here is my code

 UILabel *label = [[UILabel alloc]initWithFrame:CGRectMake(10, 50, 300, 50)];
    label.textAlignment = UITextAlignmentCenter;
    label.backgroundColor = [UIColor clearColor];
    label.textColor = [UIColor whiteColor];
    label.textColor.font = [UIFont fontWithName:@"Verdana" size:30];
    label.text = @"A very long string";
     etc...

The problems is that the font is large and can't fit in the label. It just display "A very"

What to do so entire text to be displayed. I have tried

label.lineBreakMode = UILineBreakModeWordWrap;
label.numberOfLines = 0;

But it doesn't work for me. I want to do that programmatically.

//EDIT

CGRect frame = CGRectMake(10, 50, 300, 50);
    NSString *labelString = @"Players.";

    UILabel *howManyUsersLabel = [[UILabel alloc]initWithFrame:frame];
    howManyUsersLabel.textAlignment = UITextAlignmentCenter;
    howManyUsersLabel.backgroundColor = [UIColor clearColor];
    howManyUsersLabel.textColor = [UIColor whiteColor];
    howManyUsersLabel.adjustsFontSizeToFitWidth = NO;
    howManyUsersLabel.numberOfLines = 0;

    CGFloat fontSize = 30;
    while (fontSize > 0.0)
    {
        CGSize size = [labelString sizeWithFont:[UIFont fontWithName:@"Verdana" size:fontSize] constrainedToSize:CGSizeMake(frame.size.width, 10000) lineBreakMode:UILineBreakModeWordWrap];

        if (size.height <= frame.size.height) break;
        fontSize -= 1.0;
        NSLog(@"test");
    }

    howManyUsersLabel.font = [UIFont fontWithName:@"Verdana" size:fontSize];