Google treats Facebook posts (whether they are group posts or something else) like any other web pages. But Google is limited in the amount of social web it can crawl.
These Facebook posts won't give any signal that affects search rankings unless they have high confidence, like a FB page having over 1,000 likes.
Be on Social Media not for search ranking, but to build up your presence there and drive qualified traffic to your site.
Therefore, I'll suggest NOT to waste your money paying them. Try other ways, there are many other perfect ways on building and growing your online social media presence.
Hope it helps!