Are These CV Assistances Fruitful?

To all members of this forum, I've to ask this question because I was getting so many e-mails and messages from loads of students, job seekers, and employees that if they hire online writing assistance will it be fruitful for them? as there are thousands of firms floating on the internet which are providing top-notch and professional cover letter writing, Linkedin profile writing, and other services too but how to examine that which one is the better? any kind of idea, please?