IMPORTANT: if you delete your account, it will be permanently destroyed. There is no way for Sonix to retrieve your files once you delete them.
If you are a subscriber (paid plan):
Go to https://my.sonix.ai/account/cancel to cancel your subscription
Once you have done that you can delete your entire account and its contents here: https://my.sonix.ai/account/delete
If you are on a trial:
Go to https://my.sonix.ai/account/delete to delete your entire account and its contents.