SEO
Anyone guaranteeing a ranking is telling you something untrue
Nobody controls Google's results, the ranking systems change without notice, and the competitors you are measured against are changing too. So no honest provider guarantees position one — and if someone does, that alone tells you what the rest of the engagement will be like. What can be promised is the work, and that you will be able to see what it did.
That starts with measurement, which is frequently the thing actually missing. A surprising number of businesses have paid for SEO for years with no reliable way of telling whether it worked, because analytics was never installed properly and form submissions were never tracked. Until that is fixed, everything else is opinion.