The usual conversation then.....
Forwarder : I need to get a big box to Somewhere-in-the-Boondocks
Airline : No probs, that'l cost $lots-and-lots
Forwarder : but Other-Airline will do it for $almost-nothing
Airline : OK well use Other-Airline then
Forwarder : Oh, I can't use them it doesn't fit their aircraft so they can't take it
Airline : Ah, OK, I see your point, I tell you what , when we can't take it we'll charge you $absolutely-nothing, but until then it'l cost $lots-and-lots.
repeat with variations ad nauseam