I agree with what other people are saying about this being a scam. Oftentimes, they actually can boost your follower count, but it’s mostly just bot accounts that get suspended eventually so you won’t see any real engagement from them, and you’ll notice your follower count start to dwindle as well. One of the easiest ways to grow your Instagram followers and engagement is to just promote a few posts to get people to click on your profile. If they see your stuff and like what they see, you’ll have gained a real person which is much more valuable than thousands of fake accounts.