Email support@trybackchannel.online. Write from the email address on your Backchannel account so we can find it.
Tell us which plan you bought and roughly when.
To ask for it, email support@trybackchannel.online from the email address on your Backchannel account and say you are claiming the guarantee. We reply by email.
Use Delete all my data in Settings, or ask us to close your account entirely.