Here is a comment that will actually help the poster, the Attorney General's page on the cooling off rule. As I indicated on my post a post or two up, regarding the three days notification, Florida Law only specifies "written notice" I recommend certified mail to prove that you have met the three day requirement.
Florida Attorney General - How to Protect Yourself: The Cooling-Off Rule
If you have failed to meet the three day rule your remedy is limited to a civil action against the firm, small claims...
Edit to add: The webpage does mention impossibility of performance as a reason for cancelation, or in English you are not able to receive the services contracted for.