It's funny how much I hear that from carriers on the phone - you're gonna screw me, etc.... the little accessorials usually get handled at the dispatch level. The 'what the hell happened here' orders come to me pretty quickly.
I'll repeat myself - the agreement with the 'customer' has nothing at all to do with the agreement with your carrier/supplier. Except they both use the same BOL as proof of job completion.
Bottom line is if you don't assist your suppliers with extra costs they incur doing work for you in a logical fashion, you won't have any suppliers.
Keep well,
Mike