If you have already filed, you will not be able to cancel it. If you have NOT filed nor have purchased anything, you may clear your tax information from your Account settings / Clear and start over and allow the account to go dormant. When you clear and start over, it WILL save your personal information, just not your tax information.
Here is an article to walk you through the steps of clearing and starting over, if applicable...
https://ttlc.intuit.com/replies/4248526