Error: 'Illegal characters are not allowed in form fields.' when Trying to Upgrade a Cisco Webex Meetings with Webex Teams Account

Error: 'Illegal characters are not allowed in form fields.' when trying to upgrade a Cisco Webex Meetings with Webex Teams account.

Error: 'Illegal characters are not allowed in form fields.' when entering the billing information to add a new license.

Error: 'Illegal characters are not allowed in form fields.' on the Billing Info screen.

Cause:

This error appears when the Company Name field contains special or unique characters, it appears on the Billing Info screen while upgrading a Cisco Webex Meetings with Webex Teams account.

To resolve this issue:

Log in to Cisco Webex Control Hub at https://admin.webex.com.
Click on your Company Name in the lower-left corner, then select the Info tab:
Edit the company name to remove any special or unique characters, and then select Save:

Click on the Subscriptions tab, then select Change Plan to proceed with the upgrade.