I am sent a disk with automatic billing. How do I cancel this subscription I want to download the product online through website?

I highly recommend that you just cancel the advantage program altogether and buy the program from a trusted third party seller probably for less.  The only Advantage is you get it as soon as it comes but at full price.  And then it is just a early version and there will be many updates to come.   If you can wait a little bit you can find it on sale or less at many places.  I get mine at Costco.  They usually have a coupon.  Or you might get a deal at your bank or investment company.

You can sign into your Turbo Tax Advantage account and under Your Product, select to Remove Product.  Once you remove the recurring product order, the Turbo Tax Advantage subscription will be cancelled as well.

How to cancel Turbo Tax Advantage

https://ttlc.intuit.com/community/downgrading/help/how-do-i-cancel-my-turbotax-advantage-subscription/00/25548

Also if you buy the CD you can download the program instead.  I do.  All you need is the License Code.   How to install with a License Code

https://ttlc.intuit.com/community/tax-topics/help/activating-turbotax-cd-download-software/00/852971