Whenever your client reaches out to you that SiteBizPros is reaching out to them trying to poach them by creating non existent problems, you can highlight the issued on the same emails from SiteBizPros to destroy their credibility.

"This if a well known scammer that is poaching clients from other companies by creating non existent problems about your website.

Just looking at the email they sent you, the user's name and company doesn't seem to be consistent either.

They also don't seem to have a Business Profile in Google."

Whenever you change the Primary Domain for a website, ensure you also update this in Bitrix.