This excerpt taken from the NOC 10-K filed Mar 4, 2005.
Changes in Premium Rates
We may change the premium rates from time to time with at least 31 days advance written notice to the Subscriber. No change in rates will be made until 25 months after the Policy Effective Date. An increase in rates will not be made more often than once in a 12-month period. However, We reserve the right to change rates at any time if any of the following events take place: