CSA deducting money before informing me

Are they just bluffing!!! Basically the CSA contacted us related to a child from an ex apparent they sent letters to an old address but we haven`t had anything, they jumped the gun with no contact from us and announced us that they have set up a deo, I don`t see how that is possible presumed father is not on the bc or was married to the mother of the child no dna testing was offered and yet they threaten us with a deo based on gross income without any knowledge of personal circumstances – they haven`t mentioned the name of the employer but already calculated a hefty sum can they do that? just deduct money on a say so from a woman??? with no proof.