Are you familiar with selecting service information? I'll assume so and let you work out that part.
To narrow it down to a specific company, you will want to join with client groups, i.e.
SELECT `client_groups`.`company_id`, contacts.first_name, contacts.last_name, contacts.email, contacts.country
FROM contacts
INNER JOIN `clients` ON `clients`.`id` = `contacts`.`client_id`
INNER JOIN `client_groups` ON `client_groups`.`id` = `clients`.`client_group_id`
ORDER BY `client_groups`.`company_id` ASC, contacts.country ASC;