Its time to find an alternative host rather quickly. Once Tiki has reached that boundry there is little you can do to get it back. Even deleting content in the database directly, in terms of removing pages etc wont bring it back.
Register at tiki.org and you'll be able to use the account at any *.tiki.org site, thanks to the InterTiki feature. A valid email address is required to receive site notifications and occasional newsletters. You can opt out of these items at any time.