I am indebted to Joy Hawkins for highlighting that Google has finally put into writing their advice for business owners who want to use third parties to manage their Google My Business listing (and their website visibility).
Under the heading of Deceptive Behaviour, Google says:
Guaranteeing placement on Google.
It is not possible for third-parties to influence the order in which your business appears on Google Search or Maps.
SEO Companies who guarantee
I see so many SEO websites offering #1 placements for a very cheap price... along with various testimonials from delighted customers.