How to check that your change or cancellation has been processed
If you cancel or change your plan on dropbox.com, you’ll receive an email confirmation with the subject line "Dropbox Plan will not renew" from no-reply@dropbox.com.
If you cancel or change your plan through your mobile app store, you may receive an email from that provider. If you don’t receive an email from them, we recommend contacting their support team.
To confirm your plan change or cancellation on dropbox.com, go to the Billing tab in your account settings and click Change next to Billing period. You should see a notification titled "Plan downgrade scheduled."