A few thoughts here – @jos if you recorded with the directional AND the built-in mike, is it possible you have two channels of sound, and one could be turned off?
If the iPhone main mic overrides it, do you perhaps have a digital recorder that could be used instead, or as a redundancy?
In terms of the existing files, how did you try to clean them up? There is an open source program called Audacity that is designed to, among other things, reduce background noise.
Let us know what the shop says – I agree with @ivan that we should not cross a certain threshold of efficiency in terms of how much time should be spent on cleaning them, but I wanted to get a more full sense of what the situation is with this batch, and if there is some quick tech fix.