It is not possible to downgrade a hosting package directly, but you can purchase a lower hosting package and then transfer your site to it.
To transfer your site:
- Backup all your website files through FTP or using the ‘Backup/Restore’ option in your Control Panel
- Backup any databases you have using the ‘MySQL databases’ option in your Control Panel
- Backup all your emails by connecting to the mailbox using IMAP and a mail client
- Raise a Customer Service ticket asking for the cancellation of your current hosting package
- Purchase a new hosting package
- Upload everything into the new hosting package
- Transfer your domain name over to the new package
It may take up to 24 hours for your domain name to transfer over fully.