売り手 means seller or vendor. Could it also be used in reference to the cashier, or perhaps a store clerk? Or would that not be correct because (Example: they are just in charge of collecting the money for the book that is being sold at the store?)
あの売り手にだまされました。 I was cheated by that vendor.
The guy selling that house told me he’s selling it because his neighbor is a real jerk.