The easiest way to change your test date is through your LSAC.org account. You may also use the Test Date Change form or a signed, dated, written request. Enclose a $80 payment ($81 CDN plus 5% Goods and Service Tax). The Test Date Change form (PDF) can be found on this website. Be sure that the request is received by the appropriate date, which can be found in the LSAT Dates and Deadlines section of this website.
Really? 80 dollars to change?