UITextView with scroll dynamically set resizes to default

I've implemented a ViewController that has a bottom UIView containing UITextView with scroll disabled that resizes as you type inside.

When the height of the text contained reaches 90 pixels, I enable scroll ->

scrollEnabled = YES;

What's supposed to happen: The UITextView and its superview should stay as the height that they were limited to (over the 90 pixel limit).

What happens: The UITextView resizes back to its default value.

More Info: I'm using the code of Multiline UITextField as my bottom view. I'm using iOS7.

Any help is appreciated, thank you.

EDIT: my code:

- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view from its nib.
    self.textBox.scrollEnabled = NO;
    self.textBox.font = [UIFont fontWithName:@"Helvetica" size:14];
    [self registerForKeyboardNotifications];
}

- (void)registerForKeyboardNotifications
{
    [[NSNotificationCenter defaultCenter] addObserver:self 
                                             selector:@selector(keyboardWasShown:) 
                                                 name:UIKeyboardWillShowNotification 
                                               object:nil];

    [[NSNotificationCenter defaultCenter] addObserver:self 
                                             selector:@selector(keyboardWillHide:) 
                                                 name:UIKeyboardWillHideNotification 
                                               object:nil];

    [[NSNotificationCenter defaultCenter] addObserver:self
                                             selector: @selector(keyPressed:)
                                                 name: UITextViewTextDidChangeNotification
                                               object: nil];
}

- (void)keyboardWasShown:(NSNotification *)notification
{
    NSDictionary *info = [notification userInfo];
    CGSize kbSize = [info[UIKeyboardFrameBeginUserInfoKey] CGRectValue].size;
    [self setViewMovedUp:YES byHeight:kbSize.height];
}

- (void)keyboardWillHide:(NSNotification *)notification
{
    NSDictionary *info = [notification userInfo];
    CGSize kbSize = [info[UIKeyboardFrameBeginUserInfoKey] CGRectValue].size;
    [self setViewMovedUp:NO byHeight:kbSize.height];
}

- (void)keyPressed:(id)sender
{
    CGRect textRect = [self.textBox.text boundingRectWithSize:CGSizeMake(255,MAXFLOAT) 
                                                      options:(NSStringDrawingUsesLineFragmentOrigin) 
                                                   attributes:@{NSFontAttributeName : [UIFont fontWithName:@"Helvetica" size:14]} 
                                                      context:nil];
    NSInteger newSizeH = textRect.size.height;
    if (self.textBox.hasText) {
        // if the height of our new chatbox is
        // below 90 we can set the height
        if (newSizeH <= 90) {
            self.textBox.scrollEnabled = NO;
            [self.textBox scrollRectToVisible:CGRectMake(0,0,1,1) 
                                     animated:NO];

            // chatbox
            CGRect chatBoxFrame = self.textBox.frame;
            chatBoxFrame.size.height = newSizeH + 12;
            self.textBox.frame = chatBoxFrame;

            // form view
            CGRect formFrame = self.commentBox.frame;
            formFrame.size.height = 30 + newSizeH;
            self.commentBox.frame = formFrame;
        }

        // if our new height is greater than 90
        // sets not set the height or move things
        // around and enable scrolling
        if (newSizeH > 90) {
            self.textBox.scrollEnabled = YES;
            CGRect frame = self.textBox.frame;
            frame.size.height = 102;
            self.textBox.frame = frame;
            CGRect formFrame = self.commentBox.frame;
            formFrame.size.height = 30 + 90;
            self.commentBox.frame = formFrame;
        }
    }
}

- (void)setViewMovedUp:(BOOL)movedUp byHeight:(CGFloat)height
{
    int movement = movedUp ? -height : height;
    [UIView animateWithDuration:0.3
                     animations:^{
                         self.dataView.frame = CGRectOffset(self.dataView.frame, 0.0, movement);
     }];  
}