At the written request of the pre-need purchaser, the first four thousand dollars, increased annually as provided in this section, paid by the pre-need purchaser which is placed in trust by the pre-need seller may be designated as irrevocable in accordance with the rules and regulations of the Department of Health and Human Services. The Department of Health and Human Services shall increase such amount annually on September 1 beginning with the year 2006 by the percentage change in the Consumer Price Index for All Urban Consumers published by the Federal Bureau of Labor Statistics at the close of the twelve-month period ending on August 31 of such year. Upon default or cancellation any trust funds designated as irrevocable shall be governed by section 12-1113.