I'm asking you to assume that God might exist, that your request might get heard and answered. And to make the request on those grounds. That is different from full acceptance that God is. In that sense, it's not circular.
It a way it's no different from me telling you that George Bush exists and asking you to call the White House and talk to him. What evidence do you really have that Bush exists? You've seen him on TV, but you know the tricks hollywood can do. You've heard other people talk about him, but you've heard other people talk about God too.
The only difference is that your call is much less likely to be accepted at the White House.
And if you have actually met the president then subsitute some other famous person that you haven't met.
I lost track. Is this Zeus, Thor, Jupiter, Vishnu, the Trickster Coyote, or some, as yet, unnamed god?