Saying "no" can get you into trouble in a hierarchy. There are many ways leading to no without saying "no", such as:
• I'll look into it
• I'll see what I can do
• I'll review that right away
This isn't me saying "say these things", I'm just pointing out this is an age-old problem, and saying "no" inwardly is different than saying it outwardly. Various ways of inquiring about options are also commonplace.