Can anyone guarantee page one on Google?

Why the honest answer is no

Search results are produced by a system nobody outside the company can see or control. It changes constantly, competitors respond, and the same search can return different results in two neighbouring towns on the same afternoon. Anyone guaranteeing a specific position is either misunderstanding that or hoping you do not ask.

What can honestly be guaranteed

The bill. That part is entirely within a company's control, and it is where a real guarantee belongs.

Ours is that you pay nothing until your site has held a page one position for fourteen consecutive days, and nothing at all if ninety days pass without it. That is not a softer version of a rankings guarantee. It is a stronger one, because it is a promise we can actually keep and you can actually enforce.

The question worth asking a vendor instead

Do not ask whether they guarantee page one. Ask what happens to their invoice if you never get there. If the answer is that you still pay monthly, then whatever they call their guarantee, all the risk is sitting on your side of the table.

One more thing to watch for

Some companies guarantee page one for a phrase nobody searches. Ranking first for your own business name, or for a nine word phrase with two searches a year, is easy and worthless. Ask which exact phrase is being guaranteed and what its monthly search volume is, pulled with the location set to your town.