Start by looking at the contract; it may say whether it is cancellable and on what terms (although if it does so in "fine print," there may be question whether the language is binding). Also, there are some consumer protection laws that provide cancellation periods for different types of purchases. I do not know exactly what rule, if any, would apply here, but you should be able to find some information either by (a) researching the question as a consumer protection issue on the Internet or (b) waiting for another answer to your question.