To contact support just open Mahjong and tap the game screen background, anywhere outside the tiles. A menu will appear at the bottom, along with a Brainium button in the lower lefthand corner.
If you press the Brainium button you'll see a "Contact Us" link on the following screen. After pressing that, just press "Contact Us" and in the upper right to start a chat with us about your issue. A file will be automatically attached with anonymous app information that could help us identify the cause of any freezes or crashes.