If you leave negative feedback the transport company can at any time 'cancel' the job and so the feedback also gets removed with the comment "Job cancelled by user or transport provider." even weeks after the job was in fact completed.
Also (and this really sucks) if you don't leave feedback within a set time it AUTOMATICALLY leaves POSITIVE feedback for the shipping company
so check that feedback carefully, lots of "Job cancelled by user or transport provider." means they have many unsatisfied customers.