If you ordered Kp(a) antigen testing only.
We would test, and if negative charge and report IgG DAT and the Kp(a) only. If the Kp(a) were positive we would also do the antithetical high incidence Kp(b) antigen. There would be a comment on the report saying words to the effect that no other testing was performed per your request.
the DAT is required investigational testing to validate the IAT results, and is therefore charged and reported. The reagents used in testing require QC, which is not charged or reported.
In my experience reference labs, like hospital blood banks, evolve their policies to better help meet their local customer requirements, which are varied. So talking to your reference lab manager to understand both positions may enable reaching an understanding. If that doesn’t work I guess you could, with lab director permission, refuse to pay for tests not ordered. I have however no clue of the ramifications of that course of action