It also depends on the center's regulations, in my old center techs must follow the doctor's orders exactly. They were not allowed to deviated from those orders. When I was losing weight I had similar problems with the staff.
I say similar because I would program the machine myself and set my own desired fluid removal as I was an in-center self care patient. But during their rounds the nurse would changed them back to the doctors set numbers. So it was a constant back and forth until they start to see I was correct and start to trust me. I didn't always guess right as their were times my BP would crash from too much pulling, but it happens.
Keep trying as the weight loss will greatly improve the effectiveness of dialysis and the way you feel.