The answer is simple: nobody can guarantee a top position in Google. Be aware when a party does ensure this, because they might use techniques that do not fall within Google's quality guidelines (which might give you a boost in the short term but could get you excluded from Google in the long run).
We can guarantee that our SEO audit is worth the investment and that implementing the action points will result in a better website and higher rankings in search results. Listen to what our clients have to say about it!