Просто добавьте следующий код при нажатии кнопки:
- (void) makeCall
{
NSString * mobileNumber = @"+9112345678";
UIDevice *device = [UIDevice currentDevice];
if ([[device model] isEqualToString:@"iPhone"] )
{
[[UIApplication sharedApplication] openURL:[NSURL URLWithString:[NSString stringWithFormat:@"tel:%@",mobileNumber]]];
}
else
{
UIAlertView *Notpermitted=[[UIAlertView alloc] initWithTitle:nil message:@"Your device doesn't support calling feature." delegate:nil cancelButtonTitle:@"OK" otherButtonTitles:nil];
[Notpermitted show];
}
}