Your account will automatically renew every year on the date that you signed up to use MusicDigi, and made your first payment. We do not send an email prior to charging the renewal fee, so you may just want to make sure your credit card information is up to date.
To view the date that you signed up, simply click "My account" (the little icon in the upper right) > Tap Profile. The date/time listed under "Created at" will be the date you signed up.