You can easily upgrade to the Premium or Enterprise support plan within the Zoho CRM Plus interface.
In your Zoho CRM Plus:
1.Click on the Admin photo icon in the top-right corner
2.Click Manage Billings in the Subscription section. You will be taken to the Payments page.
3.Select CRM Plus - Support Add-on to upgrade to your preferred support plan and then click Upgrade.
Another way to upgrade your support plans is by signing up priority assistance in the Help section of Zoho CRM Plus:
1. Click on the Admin photo icon in the top-right corner.
2. Click on the 24x7 Priority assistance option in the Need help? section.
3. Select the support plan (Enterprise or Premium) to upgrade to and click Upgrade.