You can click on 'Reinvest' and when you see the list for which one you want to reinvest with (SHA-256/ Scrypt) there should be an option at the top that says Do not reinvest. It should be updated within 24 hours!

Please don't, it seems they don't care and honor their contracts. Running lifetime contracts were recently reduced to one year. Looks like they can do anything. Who knows, they might say, you are done after one month on a year contract.

You should have read the terms of service contract that you signed. It states that they have the right to change contract terms. Next time read before you sighn up!

Try not using Save, but Close in the Reinvest dialog. The functions of the buttons seem to be reversed.