If you subscribe to Sonix on a monthly basis (month-to-month), you can cancel anytime. There is no annual commitment.
Note that when you cancel your subscription you lose access to your files.
You can however, purchase a storage plan to maintain access. The storage plan is $5.00 per month per 50GB. If, at some point in the future you want to re-subscribe to Sonix, you can easily do that on your account page: https://my.sonix.ai/account