To shut down your tBlog, you must do the following since there is no delete button in the controls.  This will take some time depending on how many entries/comments you have.

Make sure you have saved everything you want before you do this.

In your blog controls:

You must delete all your posts/comments one by one.

Remove/delete all your HTML codes in your sidebar.

Remove/delete all your images if you have any in your tblog account.

You can select a new template, Almo Vara as that will leave your blog completely blank.

If you have an HTML box, you can add a "robots no follow" code to remove your blog from the search engines.  If you do this, you may not be able to access the web archives to view your blog.  Make sure you have saved everything before you do this.

Although not a happy situation with the admins, you could use a redirect java script in your HTML box to your new blog.