It's a bit like nudging the doctor along to the diagnosis, procedure or treatment your research, or even your experience, suggests is appropriate. And just as there's a danger you'll antagonise your GP (even if you're right), you could easily get up the nose of the booking agent. Of course the difference is you rely on your GP for long term well-being, while your relationship with the reservation agent is transient.

But still, to get what you want it's probably best to exercise some guile. Otherwise you might be hanging up and trying again all night

So yes, I understand your caution, and it modifies the strategy I employ with booking agents. I'm aware the agent knows zillions of tons more than I do about ticketing, but if I think he/she might be missing something I'll try a nudge, perhaps on the lines of "last time I tried this, the problem turned out to be something called married segments, whartever those are: do you think that could be what's happening here?".