For a Google AdSense payment profile contact email, it may be possible to change, but it depends on the type of email and permissions on the account.
He can try this:
- Sign in to AdSense
- Go to Payments
- Open Settings / Manage settings
- Look for Payments profile or Contact information
- Edit the contact email if the option is available and save the changes
If there is no edit option, he may need to add a new user/contact email through the Google payments profile settings or contact Google AdSense support for help.
He should not pay a third party just to do this there is usually no need for a paid representative.